gin/docs/doc.md

Gin Quick Start

Contents

• Build Tags
  • Build with json replacement
  • Build without MsgPack rendering feature
• API Examples
  • Using GET, POST, PUT, PATCH, DELETE and OPTIONS
  • Parameters in path
  • Querystring parameters
  • Multipart/Urlencoded Form
  • Another example: query + post form
  • Map as querystring or postform parameters
  • Upload files
    • Single file
    • Multiple files
  • Grouping routes
  • Blank Gin without middleware by default
  • Using middleware
  • Custom Recovery behavior
  • How to write log file
  • Custom Log Format
  • Controlling Log output coloring
  • Model binding and validation
  • Custom Validators
  • Only Bind Query String
  • Bind Query String or Post Data
  • Bind Uri
  • Bind custom unmarshaler
  • Bind Header
  • Bind HTML checkboxes
  • Multipart/Urlencoded binding
  • XML, JSON, YAML, TOML and ProtoBuf rendering
    • SecureJSON
    • JSONP
    • AsciiJSON
    • PureJSON
  • Serving static files
  • Serving data from file
  • Serving data from reader
  • HTML rendering
    • Custom Template renderer
    • Custom Delimiters
    • Custom Template Funcs
  • Multitemplate
  • Redirects
  • Custom Middleware
  • Using BasicAuth() middleware
  • Goroutines inside a middleware
  • Custom HTTP configuration
  • Support Let's Encrypt
  • Run multiple service using Gin
  • Graceful shutdown or restart
    • Third-party packages
    • Manually
  • Build a single binary with templates
  • Bind form-data request with custom struct
  • Try to bind body into different structs
  • Bind form-data request with custom struct and custom tag
  • http2 server push
  • Define format for the log of routes
  • Set and get a cookie
• Don't trust all proxies
• Testing

Build tags

Build with json replacement

Gin uses encoding/json as default json package but you can change it by build from other tags.

jsoniter

go build -tags=jsoniter .

go-json

go build -tags=go_json .

sonic (you have to ensure that your cpu support avx instruction.)

$ go build -tags="sonic avx" .

Build without MsgPack rendering feature

Gin enables MsgPack rendering feature by default. But you can disable this feature by specifying nomsgpack build tag.

go build -tags=nomsgpack .

This is useful to reduce the binary size of executable files. See the detail information.

API Examples

You can find a number of ready-to-run examples at Gin examples repository.

Using GET, POST, PUT, PATCH, DELETE and OPTIONS

func main() {
  // Creates a gin router with default middleware:
  // logger and recovery (crash-free) middleware
  router := gin.Default()

  router.GET("/someGet", getting)
  router.POST("/somePost", posting)
  router.PUT("/somePut", putting)
  router.DELETE("/someDelete", deleting)
  router.PATCH("/somePatch", patching)
  router.HEAD("/someHead", head)
  router.OPTIONS("/someOptions", options)

  // By default it serves on :8080 unless a
  // PORT environment variable was defined.
  router.Run()
  // router.Run(":3000") for a hard coded port
}

Parameters in path

func main() {
  router := gin.Default()

  // This handler will match /user/john but will not match /user/ or /user
  router.GET("/user/:name", func(c *gin.Context) {
    name := c.Param("name")
    c.String(http.StatusOK, "Hello %s", name)
  })

  // However, this one will match /user/john/ and also /user/john/send
  // If no other routers match /user/john, it will redirect to /user/john/
  router.GET("/user/:name/*action", func(c *gin.Context) {
    name := c.Param("name")
    action := c.Param("action")
    message := name + " is " + action
    c.String(http.StatusOK, message)
  })

  // For each matched request Context will hold the route definition
  router.POST("/user/:name/*action", func(c *gin.Context) {
    b := c.FullPath() == "/user/:name/*action" // true
    c.String(http.StatusOK, "%t", b)
  })

  // This handler will add a new router for /user/groups.
  // Exact routes are resolved before param routes, regardless of the order they were defined.
  // Routes starting with /user/groups are never interpreted as /user/:name/... routes
  router.GET("/user/groups", func(c *gin.Context) {
    c.String(http.StatusOK, "The available groups are [...]")
  })

  router.Run(":8080")
}

Querystring parameters

func main() {
  router := gin.Default()

  // Query string parameters are parsed using the existing underlying request object.
  // The request responds to an url matching:  /welcome?firstname=Jane&lastname=Doe
  router.GET("/welcome", func(c *gin.Context) {
    firstname := c.DefaultQuery("firstname", "Guest")
    lastname := c.Query("lastname") // shortcut for c.Request.URL.Query().Get("lastname")

    c.String(http.StatusOK, "Hello %s %s", firstname, lastname)
  })
  router.Run(":8080")
}

Multipart/Urlencoded Form

func main() {
  router := gin.Default()

  router.POST("/form_post", func(c *gin.Context) {
    message := c.PostForm("message")
    nick := c.DefaultPostForm("nick", "anonymous")

    c.JSON(http.StatusOK, gin.H{
      "status":  "posted",
      "message": message,
      "nick":    nick,
    })
  })
  router.Run(":8080")
}

Another example: query + post form

POST /post?id=1234&page=1 HTTP/1.1
Content-Type: application/x-www-form-urlencoded

name=manu&message=this_is_great

func main() {
  router := gin.Default()

  router.POST("/post", func(c *gin.Context) {

    id := c.Query("id")
    page := c.DefaultQuery("page", "0")
    name := c.PostForm("name")
    message := c.PostForm("message")

    fmt.Printf("id: %s; page: %s; name: %s; message: %s", id, page, name, message)
  })
  router.Run(":8080")
}

id: 1234; page: 1; name: manu; message: this_is_great

Map as querystring or postform parameters

POST /post?ids[a]=1234&ids[b]=hello HTTP/1.1
Content-Type: application/x-www-form-urlencoded

names[first]=thinkerou&names[second]=tianou

func main() {
  router := gin.Default()

  router.POST("/post", func(c *gin.Context) {

    ids := c.QueryMap("ids")
    names := c.PostFormMap("names")

    fmt.Printf("ids: %v; names: %v", ids, names)
  })
  router.Run(":8080")
}

ids: map[b:hello a:1234]; names: map[second:tianou first:thinkerou]

Upload files

Single file

References issue #774 and detail example code.

file.Filename SHOULD NOT be trusted. See Content-Disposition on MDN and #1693

The filename is always optional and must not be used blindly by the application: path information should be stripped, and conversion to the server file system rules should be done.

func main() {
  router := gin.Default()
  // Set a lower memory limit for multipart forms (default is 32 MiB)
  router.MaxMultipartMemory = 8 << 20  // 8 MiB
  router.POST("/upload", func(c *gin.Context) {
    // Single file
    file, _ := c.FormFile("file")
    log.Println(file.Filename)

    // Upload the file to specific dst.
    c.SaveUploadedFile(file, dst)

    c.String(http.StatusOK, fmt.Sprintf("'%s' uploaded!", file.Filename))
  })
  router.Run(":8080")
}

How to curl:

curl -X POST http://localhost:8080/upload \
  -F "file=@/Users/appleboy/test.zip" \
  -H "Content-Type: multipart/form-data"

Multiple files

See the detail example code.

func main() {
  router := gin.Default()
  // Set a lower memory limit for multipart forms (default is 32 MiB)
  router.MaxMultipartMemory = 8 << 20  // 8 MiB
  router.POST("/upload", func(c *gin.Context) {
    // Multipart form
    form, _ := c.MultipartForm()
    files := form.File["upload[]"]

    for _, file := range files {
      log.Println(file.Filename)

      // Upload the file to specific dst.
      c.SaveUploadedFile(file, dst)
    }
    c.String(http.StatusOK, fmt.Sprintf("%d files uploaded!", len(files)))
  })
  router.Run(":8080")
}

How to curl:

curl -X POST http://localhost:8080/upload \
  -F "upload[]=@/Users/appleboy/test1.zip" \
  -F "upload[]=@/Users/appleboy/test2.zip" \
  -H "Content-Type: multipart/form-data"

Grouping routes

func main() {
  router := gin.Default()

  // Simple group: v1
  v1 := router.Group("/v1")
  {
    v1.POST("/login", loginEndpoint)
    v1.POST("/submit", submitEndpoint)
    v1.POST("/read", readEndpoint)
  }

  // Simple group: v2
  v2 := router.Group("/v2")
  {
    v2.POST("/login", loginEndpoint)
    v2.POST("/submit", submitEndpoint)
    v2.POST("/read", readEndpoint)
  }

  router.Run(":8080")
}

Blank Gin without middleware by default

Use

r := gin.New()

instead of

// Default With the Logger and Recovery middleware already attached
r := gin.Default()

Using middleware

func main() {
  // Creates a router without any middleware by default
  r := gin.New()

  // Global middleware
  // Logger middleware will write the logs to gin.DefaultWriter even if you set with GIN_MODE=release.
  // By default gin.DefaultWriter = os.Stdout
  r.Use(gin.Logger())

  // Recovery middleware recovers from any panics and writes a 500 if there was one.
  r.Use(gin.Recovery())

  // Per route middleware, you can add as many as you desire.
  r.GET("/benchmark", MyBenchLogger(), benchEndpoint)

  // Authorization group
  // authorized := r.Group("/", AuthRequired())
  // exactly the same as:
  authorized := r.Group("/")
  // per group middleware! in this case we use the custom created
  // AuthRequired() middleware just in the "authorized" group.
  authorized.Use(AuthRequired())
  {
    authorized.POST("/login", loginEndpoint)
    authorized.POST("/submit", submitEndpoint)
    authorized.POST("/read", readEndpoint)

    // nested group
    testing := authorized.Group("testing")
    // visit 0.0.0.0:8080/testing/analytics
    testing.GET("/analytics", analyticsEndpoint)
  }

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Custom Recovery behavior

func main() {
  // Creates a router without any middleware by default
  r := gin.New()

  // Global middleware
  // Logger middleware will write the logs to gin.DefaultWriter even if you set with GIN_MODE=release.
  // By default gin.DefaultWriter = os.Stdout
  r.Use(gin.Logger())

  // Recovery middleware recovers from any panics and writes a 500 if there was one.
  r.Use(gin.CustomRecovery(func(c *gin.Context, recovered any) {
    if err, ok := recovered.(string); ok {
      c.String(http.StatusInternalServerError, fmt.Sprintf("error: %s", err))
    }
    c.AbortWithStatus(http.StatusInternalServerError)
  }))

  r.GET("/panic", func(c *gin.Context) {
    // panic with a string -- the custom middleware could save this to a database or report it to the user
    panic("foo")
  })

  r.GET("/", func(c *gin.Context) {
    c.String(http.StatusOK, "ohai")
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

How to write log file

func main() {
  // Disable Console Color, you don't need console color when writing the logs to file.
  gin.DisableConsoleColor()

  // Logging to a file.
  f, _ := os.Create("gin.log")
  gin.DefaultWriter = io.MultiWriter(f)

  // Use the following code if you need to write the logs to file and console at the same time.
  // gin.DefaultWriter = io.MultiWriter(f, os.Stdout)

  router := gin.Default()
  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

   router.Run(":8080")
}

Custom Log Format

func main() {
  router := gin.New()

  // LoggerWithFormatter middleware will write the logs to gin.DefaultWriter
  // By default gin.DefaultWriter = os.Stdout
  router.Use(gin.LoggerWithFormatter(func(param gin.LogFormatterParams) string {

    // your custom format
    return fmt.Sprintf("%s - [%s] \"%s %s %s %d %s \"%s\" %s\"\n",
        param.ClientIP,
        param.TimeStamp.Format(time.RFC1123),
        param.Method,
        param.Path,
        param.Request.Proto,
        param.StatusCode,
        param.Latency,
        param.Request.UserAgent(),
        param.ErrorMessage,
    )
  }))
  router.Use(gin.Recovery())

  router.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })

  router.Run(":8080")
}

Sample Output

::1 - [Fri, 07 Dec 2018 17:04:38 JST] "GET /ping HTTP/1.1 200 122.767µs "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36" "

Skip logging

func main() {
  router := gin.New()
  
  // skip logging for desired paths by setting SkipPaths in LoggerConfig
  loggerConfig := gin.LoggerConfig{SkipPaths: []string{"/metrics"}}
  
  // skip logging based on your logic by setting Skip func in LoggerConfig
  loggerConfig.Skip = func(c *gin.Context) bool {
      // as an example skip non server side errors
      return c.Writer.Status() < http.StatusInternalServerError
  }
  
  engine.Use(gin.LoggerWithConfig(loggerConfig))
  router.Use(gin.Recovery())
  
  // skipped
  router.GET("/metrics", func(c *gin.Context) {
      c.Status(http.StatusNotImplemented)
  })

  // skipped
  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

  // not skipped
  router.GET("/data", func(c *gin.Context) {
    c.Status(http.StatusNotImplemented)
  })
  
  router.Run(":8080")
}

Controlling Log output coloring

By default, logs output on console should be colorized depending on the detected TTY.

Never colorize logs:

func main() {
  // Disable log's color
  gin.DisableConsoleColor()

  // Creates a gin router with default middleware:
  // logger and recovery (crash-free) middleware
  router := gin.Default()

  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

  router.Run(":8080")
}

Always colorize logs:

func main() {
  // Force log's color
  gin.ForceConsoleColor()

  // Creates a gin router with default middleware:
  // logger and recovery (crash-free) middleware
  router := gin.Default()

  router.GET("/ping", func(c *gin.Context) {
      c.String(http.StatusOK, "pong")
  })

  router.Run(":8080")
}

Model binding and validation

To bind a request body into a type, use model binding. We currently support binding of JSON, XML, YAML, TOML and standard form values (foo=bar&boo=baz).

Gin uses go-playground/validator/v10 for validation. Check the full docs on tags usage here.

Note that you need to set the corresponding binding tag on all fields you want to bind. For example, when binding from JSON, set json:"fieldname".

Also, Gin provides two sets of methods for binding:

• Type - Must bind
  • Methods - Bind, BindJSON, BindXML, BindQuery, BindYAML, BindHeader, BindTOML
  • Behavior - These methods use MustBindWith under the hood. If there is a binding error, the request is aborted with c.AbortWithError(400, err).SetType(ErrorTypeBind). This sets the response status code to 400 and the Content-Type header is set to text/plain; charset=utf-8. Note that if you try to set the response code after this, it will result in a warning [GIN-debug] [WARNING] Headers were already written. Wanted to override status code 400 with 422. If you wish to have greater control over the behavior, consider using the ShouldBind equivalent method.
• Type - Should bind
  • Methods - ShouldBind, ShouldBindJSON, ShouldBindXML, ShouldBindQuery, ShouldBindYAML, ShouldBindHeader, ShouldBindTOML,
  • Behavior - These methods use ShouldBindWith under the hood. If there is a binding error, the error is returned and it is the developer's responsibility to handle the request and error appropriately.

When using the Bind-method, Gin tries to infer the binder depending on the Content-Type header. If you are sure what you are binding, you can use MustBindWith or ShouldBindWith.

You can also specify that specific fields are required. If a field is decorated with binding:"required" and has an empty value when binding, an error will be returned.

// Binding from JSON
type Login struct {
  User     string `form:"user" json:"user" xml:"user"  binding:"required"`
  Password string `form:"password" json:"password" xml:"password" binding:"required"`
}

func main() {
  router := gin.Default()

  // Example for binding JSON ({"user": "manu", "password": "123"})
  router.POST("/loginJSON", func(c *gin.Context) {
    var json Login
    if err := c.ShouldBindJSON(&json); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }

    if json.User != "manu" || json.Password != "123" {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
      return
    }

    c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
  })

  // Example for binding XML (
  //  <?xml version="1.0" encoding="UTF-8"?>
  //  <root>
  //    <user>manu</user>
  //    <password>123</password>
  //  </root>)
  router.POST("/loginXML", func(c *gin.Context) {
    var xml Login
    if err := c.ShouldBindXML(&xml); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }

    if xml.User != "manu" || xml.Password != "123" {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
      return
    }

    c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
  })

  // Example for binding a HTML form (user=manu&password=123)
  router.POST("/loginForm", func(c *gin.Context) {
    var form Login
    // This will infer what binder to use depending on the content-type header.
    if err := c.ShouldBind(&form); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
      return
    }

    if form.User != "manu" || form.Password != "123" {
      c.JSON(http.StatusUnauthorized, gin.H{"status": "unauthorized"})
      return
    }

    c.JSON(http.StatusOK, gin.H{"status": "you are logged in"})
  })

  // Listen and serve on 0.0.0.0:8080
  router.Run(":8080")
}

Sample request

$ curl -v -X POST \
  http://localhost:8080/loginJSON \
  -H 'content-type: application/json' \
  -d '{ "user": "manu" }'
> POST /loginJSON HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.51.0
> Accept: */*
> content-type: application/json
> Content-Length: 18
>
* upload completely sent off: 18 out of 18 bytes
< HTTP/1.1 400 Bad Request
< Content-Type: application/json; charset=utf-8
< Date: Fri, 04 Aug 2017 03:51:31 GMT
< Content-Length: 100
<
{"error":"Key: 'Login.Password' Error:Field validation for 'Password' failed on the 'required' tag"}

Skip validate: when running the above example using the above the curl command, it returns error. Because the example use binding:"required" for Password. If use binding:"-" for Password, then it will not return error when running the above example again.

Custom Validators

It is also possible to register custom validators. See the example code.

package main

import (
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
  "github.com/gin-gonic/gin/binding"
  "github.com/go-playground/validator/v10"
)

// Booking contains binded and validated data.
type Booking struct {
  CheckIn  time.Time `form:"check_in" binding:"required,bookabledate" time_format:"2006-01-02"`
  CheckOut time.Time `form:"check_out" binding:"required,gtfield=CheckIn" time_format:"2006-01-02"`
}

var bookableDate validator.Func = func(fl validator.FieldLevel) bool {
  date, ok := fl.Field().Interface().(time.Time)
  if ok {
    today := time.Now()
    if today.After(date) {
      return false
    }
  }
  return true
}

func main() {
  route := gin.Default()

  if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
    v.RegisterValidation("bookabledate", bookableDate)
  }

  route.GET("/bookable", getBookable)
  route.Run(":8085")
}

func getBookable(c *gin.Context) {
  var b Booking
  if err := c.ShouldBindWith(&b, binding.Query); err == nil {
    c.JSON(http.StatusOK, gin.H{"message": "Booking dates are valid!"})
  } else {
    c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
  }
}

$ curl "localhost:8085/bookable?check_in=2030-04-16&check_out=2030-04-17"
{"message":"Booking dates are valid!"}

$ curl "localhost:8085/bookable?check_in=2030-03-10&check_out=2030-03-09"
{"error":"Key: 'Booking.CheckOut' Error:Field validation for 'CheckOut' failed on the 'gtfield' tag"}

$ curl "localhost:8085/bookable?check_in=2000-03-09&check_out=2000-03-10"
{"error":"Key: 'Booking.CheckIn' Error:Field validation for 'CheckIn' failed on the 'bookabledate' tag"}%

Struct level validations can also be registered this way. See the struct-lvl-validation example to learn more.

Only Bind Query String

ShouldBindQuery function only binds the query params and not the post data. See the detail information.

package main

import (
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

type Person struct {
  Name    string `form:"name"`
  Address string `form:"address"`
}

func main() {
  route := gin.Default()
  route.Any("/testing", startPage)
  route.Run(":8085")
}

func startPage(c *gin.Context) {
  var person Person
  if c.ShouldBindQuery(&person) == nil {
    log.Println("====== Only Bind By Query String ======")
    log.Println(person.Name)
    log.Println(person.Address)
  }
  c.String(http.StatusOK, "Success")
}

Bind Query String or Post Data

See the detail information.

package main

import (
  "log"
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
)

type Person struct {
  Name       string    `form:"name"`
  Address    string    `form:"address"`
  Birthday   time.Time `form:"birthday" time_format:"2006-01-02" time_utc:"1"`
  CreateTime time.Time `form:"createTime" time_format:"unixNano"`
  UnixTime   time.Time `form:"unixTime" time_format:"unix"`
}

func main() {
  route := gin.Default()
  route.GET("/testing", startPage)
  route.Run(":8085")
}

func startPage(c *gin.Context) {
  var person Person
  // If `GET`, only `Form` binding engine (`query`) used.
  // If `POST`, first checks the `content-type` for `JSON` or `XML`, then uses `Form` (`form-data`).
  // See more at https://github.com/gin-gonic/gin/blob/master/binding/binding.go#L88
  if c.ShouldBind(&person) == nil {
    log.Println(person.Name)
    log.Println(person.Address)
    log.Println(person.Birthday)
    log.Println(person.CreateTime)
    log.Println(person.UnixTime)
  }

  c.String(http.StatusOK, "Success")
}

Test it with:

curl -X GET "localhost:8085/testing?name=appleboy&address=xyz&birthday=1992-03-15&createTime=1562400033000000123&unixTime=1562400033"

Bind Uri

See the detail information.

package main

import (
  "net/http"

  "github.com/gin-gonic/gin"
)

type Person struct {
  ID string `uri:"id" binding:"required,uuid"`
  Name string `uri:"name" binding:"required"`
}

func main() {
  route := gin.Default()
  route.GET("/:name/:id", func(c *gin.Context) {
    var person Person
    if err := c.ShouldBindUri(&person); err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"msg": err.Error()})
      return
    }
    c.JSON(http.StatusOK, gin.H{"name": person.Name, "uuid": person.ID})
  })
  route.Run(":8088")
}

Test it with:

curl -v localhost:8088/thinkerou/987fbc97-4bed-5078-9f07-9141ba07c9f3
curl -v localhost:8088/thinkerou/not-uuid

Bind custom unmarshaler

package main

import (
  "github.com/gin-gonic/gin"
  "strings"
)

type Birthday string

func (b *Birthday) UnmarshalParam(param string) error {
  *b = Birthday(strings.Replace(param, "-", "/", -1))
  return nil
}

func main() {
  route := gin.Default()
  var request struct {
    Birthday Birthday `form:"birthday"`
  }
  route.GET("/test", func(ctx *gin.Context) {
    _ = ctx.BindQuery(&request)
    ctx.JSON(200, request.Birthday)
  })
  route.Run(":8088")
}

Test it with:

curl 'localhost:8088/test?birthday=2000-01-01'

Result

"2000/01/01"

Bind Header

package main

import (
  "fmt"
  "net/http"

  "github.com/gin-gonic/gin"
)

type testHeader struct {
  Rate   int    `header:"Rate"`
  Domain string `header:"Domain"`
}

func main() {
  r := gin.Default()
  r.GET("/", func(c *gin.Context) {
    h := testHeader{}

    if err := c.ShouldBindHeader(&h); err != nil {
      c.JSON(http.StatusOK, err)
    }

    fmt.Printf("%#v\n", h)
    c.JSON(http.StatusOK, gin.H{"Rate": h.Rate, "Domain": h.Domain})
  })

  r.Run()

// client
// curl -H "rate:300" -H "domain:music" 127.0.0.1:8080/
// output
// {"Domain":"music","Rate":300}
}

Bind HTML checkboxes

See the detail information

main.go

...

type myForm struct {
    Colors []string `form:"colors[]"`
}

...

func formHandler(c *gin.Context) {
    var fakeForm myForm
    c.ShouldBind(&fakeForm)
    c.JSON(http.StatusOK, gin.H{"color": fakeForm.Colors})
}

...

form.html

<form action="/" method="POST">
    <p>Check some colors</p>
    <label for="red">Red</label>
    <input type="checkbox" name="colors[]" value="red" id="red">
    <label for="green">Green</label>
    <input type="checkbox" name="colors[]" value="green" id="green">
    <label for="blue">Blue</label>
    <input type="checkbox" name="colors[]" value="blue" id="blue">
    <input type="submit">
</form>

result:

{"color":["red","green","blue"]}

Multipart/Urlencoded binding

type ProfileForm struct {
  Name   string                `form:"name" binding:"required"`
  Avatar *multipart.FileHeader `form:"avatar" binding:"required"`

  // or for multiple files
  // Avatars []*multipart.FileHeader `form:"avatar" binding:"required"`
}

func main() {
  router := gin.Default()
  router.POST("/profile", func(c *gin.Context) {
    // you can bind multipart form with explicit binding declaration:
    // c.ShouldBindWith(&form, binding.Form)
    // or you can simply use autobinding with ShouldBind method:
    var form ProfileForm
    // in this case proper binding will be automatically selected
    if err := c.ShouldBind(&form); err != nil {
      c.String(http.StatusBadRequest, "bad request")
      return
    }

    err := c.SaveUploadedFile(form.Avatar, form.Avatar.Filename)
    if err != nil {
      c.String(http.StatusInternalServerError, "unknown error")
      return
    }

    // db.Save(&form)

    c.String(http.StatusOK, "ok")
  })
  router.Run(":8080")
}

Test it with:

curl -X POST -v --form name=user --form "avatar=@./avatar.png" http://localhost:8080/profile

XML, JSON, YAML, TOML and ProtoBuf rendering

func main() {
  r := gin.Default()

  // gin.H is a shortcut for map[string]any
  r.GET("/someJSON", func(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/moreJSON", func(c *gin.Context) {
    // You also can use a struct
    var msg struct {
      Name    string `json:"user"`
      Message string
      Number  int
    }
    msg.Name = "Lena"
    msg.Message = "hey"
    msg.Number = 123
    // Note that msg.Name becomes "user" in the JSON
    // Will output  :   {"user": "Lena", "Message": "hey", "Number": 123}
    c.JSON(http.StatusOK, msg)
  })

  r.GET("/someXML", func(c *gin.Context) {
    c.XML(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/someYAML", func(c *gin.Context) {
    c.YAML(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/someTOML", func(c *gin.Context) {
    c.TOML(http.StatusOK, gin.H{"message": "hey", "status": http.StatusOK})
  })

  r.GET("/someProtoBuf", func(c *gin.Context) {
    reps := []int64{int64(1), int64(2)}
    label := "test"
    // The specific definition of protobuf is written in the testdata/protoexample file.
    data := &protoexample.Test{
      Label: &label,
      Reps:  reps,
    }
    // Note that data becomes binary data in the response
    // Will output protoexample.Test protobuf serialized data
    c.ProtoBuf(http.StatusOK, data)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

SecureJSON

Using SecureJSON to prevent json hijacking. Default prepends "while(1)," to response body if the given struct is array values.

func main() {
  r := gin.Default()

  // You can also use your own secure json prefix
  // r.SecureJsonPrefix(")]}',\n")

  r.GET("/someJSON", func(c *gin.Context) {
    names := []string{"lena", "austin", "foo"}

    // Will output  :   while(1);["lena","austin","foo"]
    c.SecureJSON(http.StatusOK, names)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

JSONP

Using JSONP to request data from a server in a different domain. Add callback to response body if the query parameter callback exists.

func main() {
  r := gin.Default()

  r.GET("/JSONP", func(c *gin.Context) {
    data := gin.H{
      "foo": "bar",
    }

    //callback is x
    // Will output  :   x({\"foo\":\"bar\"})
    c.JSONP(http.StatusOK, data)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")

        // client
        // curl http://127.0.0.1:8080/JSONP?callback=x
}

AsciiJSON

Using AsciiJSON to Generates ASCII-only JSON with escaped non-ASCII characters.

func main() {
  r := gin.Default()

  r.GET("/someJSON", func(c *gin.Context) {
    data := gin.H{
      "lang": "GO语言",
      "tag":  "<br>",
    }

    // will output : {"lang":"GO\u8bed\u8a00","tag":"\u003cbr\u003e"}
    c.AsciiJSON(http.StatusOK, data)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

PureJSON

Normally, JSON replaces special HTML characters with their unicode entities, e.g. < becomes \u003c. If you want to encode such characters literally, you can use PureJSON instead. This feature is unavailable in Go 1.6 and lower.

func main() {
  r := gin.Default()

  // Serves unicode entities
  r.GET("/json", func(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{
      "html": "<b>Hello, world!</b>",
    })
  })

  // Serves literal characters
  r.GET("/purejson", func(c *gin.Context) {
    c.PureJSON(http.StatusOK, gin.H{
      "html": "<b>Hello, world!</b>",
    })
  })

  // listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Serving static files

func main() {
  router := gin.Default()
  router.Static("/assets", "./assets")
  router.StaticFS("/more_static", http.Dir("my_file_system"))
  router.StaticFile("/favicon.ico", "./resources/favicon.ico")
  router.StaticFileFS("/more_favicon.ico", "more_favicon.ico", http.Dir("my_file_system"))
  
  // Listen and serve on 0.0.0.0:8080
  router.Run(":8080")
}

Serving data from file

func main() {
  router := gin.Default()

  router.GET("/local/file", func(c *gin.Context) {
    c.File("local/file.go")
  })

  var fs http.FileSystem = // ...
  router.GET("/fs/file", func(c *gin.Context) {
    c.FileFromFS("fs/file.go", fs)
  })
}

Serving data from reader

func main() {
  router := gin.Default()
  router.GET("/someDataFromReader", func(c *gin.Context) {
    response, err := http.Get("https://raw.githubusercontent.com/gin-gonic/logo/master/color.png")
    if err != nil || response.StatusCode != http.StatusOK {
      c.Status(http.StatusServiceUnavailable)
      return
    }

    reader := response.Body
     defer reader.Close()
    contentLength := response.ContentLength
    contentType := response.Header.Get("Content-Type")

    extraHeaders := map[string]string{
      "Content-Disposition": `attachment; filename="gopher.png"`,
    }

    c.DataFromReader(http.StatusOK, contentLength, contentType, reader, extraHeaders)
  })
  router.Run(":8080")
}

HTML rendering

Using LoadHTMLGlob() or LoadHTMLFiles()

func main() {
  router := gin.Default()
  router.LoadHTMLGlob("templates/*")
  //router.LoadHTMLFiles("templates/template1.html", "templates/template2.html")
  router.GET("/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "index.tmpl", gin.H{
      "title": "Main website",
    })
  })
  router.Run(":8080")
}

templates/index.tmpl

<html>
  <h1>
    {{ .title }}
  </h1>
</html>

Using templates with same name in different directories

func main() {
  router := gin.Default()
  router.LoadHTMLGlob("templates/**/*")
  router.GET("/posts/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "posts/index.tmpl", gin.H{
      "title": "Posts",
    })
  })
  router.GET("/users/index", func(c *gin.Context) {
    c.HTML(http.StatusOK, "users/index.tmpl", gin.H{
      "title": "Users",
    })
  })
  router.Run(":8080")
}

templates/posts/index.tmpl

{{ define "posts/index.tmpl" }}
<html><h1>
  {{ .title }}
</h1>
<p>Using posts/index.tmpl</p>
</html>
{{ end }}

templates/users/index.tmpl

{{ define "users/index.tmpl" }}
<html><h1>
  {{ .title }}
</h1>
<p>Using users/index.tmpl</p>
</html>
{{ end }}

Custom Template renderer

You can also use your own html template render

import "html/template"

func main() {
  router := gin.Default()
  html := template.Must(template.ParseFiles("file1", "file2"))
  router.SetHTMLTemplate(html)
  router.Run(":8080")
}

Custom Delimiters

You may use custom delims

  r := gin.Default()
  r.Delims("{[{", "}]}")
  r.LoadHTMLGlob("/path/to/templates")

Custom Template Funcs

See the detail example code.

main.go

import (
  "fmt"
  "html/template"
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
)

func formatAsDate(t time.Time) string {
  year, month, day := t.Date()
  return fmt.Sprintf("%d/%02d/%02d", year, month, day)
}

func main() {
  router := gin.Default()
  router.Delims("{[{", "}]}")
  router.SetFuncMap(template.FuncMap{
      "formatAsDate": formatAsDate,
  })
  router.LoadHTMLFiles("./testdata/template/raw.tmpl")

  router.GET("/raw", func(c *gin.Context) {
      c.HTML(http.StatusOK, "raw.tmpl", gin.H{
          "now": time.Date(2017, 07, 01, 0, 0, 0, 0, time.UTC),
      })
  })

  router.Run(":8080")
}

raw.tmpl

Date: {[{.now | formatAsDate}]}

Result:

Date: 2017/07/01

Multitemplate

Gin allow by default use only one html.Template. Check a multitemplate render for using features like go 1.6 block template.

Redirects

Issuing a HTTP redirect is easy. Both internal and external locations are supported.

r.GET("/test", func(c *gin.Context) {
  c.Redirect(http.StatusMovedPermanently, "http://www.google.com/")
})

Issuing a HTTP redirect from POST. Refer to issue: #444

r.POST("/test", func(c *gin.Context) {
  c.Redirect(http.StatusFound, "/foo")
})

Issuing a Router redirect, use HandleContext like below.

r.GET("/test", func(c *gin.Context) {
    c.Request.URL.Path = "/test2"
    r.HandleContext(c)
})
r.GET("/test2", func(c *gin.Context) {
    c.JSON(http.StatusOK, gin.H{"hello": "world"})
})

Custom Middleware

func Logger() gin.HandlerFunc {
  return func(c *gin.Context) {
    t := time.Now()

    // Set example variable
    c.Set("example", "12345")

    // before request

    c.Next()

    // after request
    latency := time.Since(t)
    log.Print(latency)

    // access the status we are sending
    status := c.Writer.Status()
    log.Println(status)
  }
}

func main() {
  r := gin.New()
  r.Use(Logger())

  r.GET("/test", func(c *gin.Context) {
    example := c.MustGet("example").(string)

    // it would print: "12345"
    log.Println(example)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Using BasicAuth() middleware

// simulate some private data
var secrets = gin.H{
  "foo":    gin.H{"email": "foo@bar.com", "phone": "123433"},
  "austin": gin.H{"email": "austin@example.com", "phone": "666"},
  "lena":   gin.H{"email": "lena@guapa.com", "phone": "523443"},
}

func main() {
  r := gin.Default()

  // Group using gin.BasicAuth() middleware
  // gin.Accounts is a shortcut for map[string]string
  authorized := r.Group("/admin", gin.BasicAuth(gin.Accounts{
    "foo":    "bar",
    "austin": "1234",
    "lena":   "hello2",
    "manu":   "4321",
  }))

  // /admin/secrets endpoint
  // hit "localhost:8080/admin/secrets
  authorized.GET("/secrets", func(c *gin.Context) {
    // get user, it was set by the BasicAuth middleware
    user := c.MustGet(gin.AuthUserKey).(string)
    if secret, ok := secrets[user]; ok {
      c.JSON(http.StatusOK, gin.H{"user": user, "secret": secret})
    } else {
      c.JSON(http.StatusOK, gin.H{"user": user, "secret": "NO SECRET :("})
    }
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Goroutines inside a middleware

When starting new Goroutines inside a middleware or handler, you SHOULD NOT use the original context inside it, you have to use a read-only copy.

func main() {
  r := gin.Default()

  r.GET("/long_async", func(c *gin.Context) {
    // create copy to be used inside the goroutine
    cCp := c.Copy()
    go func() {
      // simulate a long task with time.Sleep(). 5 seconds
      time.Sleep(5 * time.Second)

      // note that you are using the copied context "cCp", IMPORTANT
      log.Println("Done! in path " + cCp.Request.URL.Path)
    }()
  })

  r.GET("/long_sync", func(c *gin.Context) {
    // simulate a long task with time.Sleep(). 5 seconds
    time.Sleep(5 * time.Second)

    // since we are NOT using a goroutine, we do not have to copy the context
    log.Println("Done! in path " + c.Request.URL.Path)
  })

  // Listen and serve on 0.0.0.0:8080
  r.Run(":8080")
}

Custom HTTP configuration

Use http.ListenAndServe() directly, like this:

func main() {
  router := gin.Default()
  http.ListenAndServe(":8080", router)
}

or

func main() {
  router := gin.Default()

  s := &http.Server{
    Addr:           ":8080",
    Handler:        router,
    ReadTimeout:    10 * time.Second,
    WriteTimeout:   10 * time.Second,
    MaxHeaderBytes: 1 << 20,
  }
  s.ListenAndServe()
}

Support Let's Encrypt

example for 1-line LetsEncrypt HTTPS servers.

package main

import (
  "log"
  "net/http"

  "github.com/gin-gonic/autotls"
  "github.com/gin-gonic/gin"
)

func main() {
  r := gin.Default()

  // Ping handler
  r.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })

  log.Fatal(autotls.Run(r, "example1.com", "example2.com"))
}

example for custom autocert manager.

package main

import (
  "log"
  "net/http"

  "github.com/gin-gonic/autotls"
  "github.com/gin-gonic/gin"
  "golang.org/x/crypto/acme/autocert"
)

func main() {
  r := gin.Default()

  // Ping handler
  r.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })

  m := autocert.Manager{
    Prompt:     autocert.AcceptTOS,
    HostPolicy: autocert.HostWhitelist("example1.com", "example2.com"),
    Cache:      autocert.DirCache("/var/www/.cache"),
  }

  log.Fatal(autotls.RunWithManager(r, &m))
}

Run multiple service using Gin

See the question and try the following example:

package main

import (
  "log"
  "net/http"
  "time"

  "github.com/gin-gonic/gin"
  "golang.org/x/sync/errgroup"
)

var (
  g errgroup.Group
)

func router01() http.Handler {
  e := gin.New()
  e.Use(gin.Recovery())
  e.GET("/", func(c *gin.Context) {
    c.JSON(
      http.StatusOK,
      gin.H{
        "code":  http.StatusOK,
        "error": "Welcome server 01",
      },
    )
  })

  return e
}

func router02() http.Handler {
  e := gin.New()
  e.Use(gin.Recovery())
  e.GET("/", func(c *gin.Context) {
    c.JSON(
      http.StatusOK,
      gin.H{
        "code":  http.StatusOK,
        "error": "Welcome server 02",
      },
    )
  })

  return e
}

func main() {
  server01 := &http.Server{
    Addr:         ":8080",
    Handler:      router01(),
    ReadTimeout:  5 * time.Second,
    WriteTimeout: 10 * time.Second,
  }

  server02 := &http.Server{
    Addr:         ":8081",
    Handler:      router02(),
    ReadTimeout:  5 * time.Second,
    WriteTimeout: 10 * time.Second,
  }

  g.Go(func() error {
    err := server01.ListenAndServe()
    if err != nil && err != http.ErrServerClosed {
      log.Fatal(err)
    }
    return err
  })

  g.Go(func() error {
    err := server02.ListenAndServe()
    if err != nil && err != http.ErrServerClosed {
      log.Fatal(err)
    }
    return err
  })

  if err := g.Wait(); err != nil {
    log.Fatal(err)
  }
}

Graceful shutdown or restart

There are a few approaches you can use to perform a graceful shutdown or restart. You can make use of third-party packages specifically built for that, or you can manually do the same with the functions and methods from the built-in packages.

Third-party packages

We can use fvbock/endless to replace the default ListenAndServe. Refer to issue #296 for more details.

router := gin.Default()
router.GET("/", handler)
// [...]
endless.ListenAndServe(":4242", router)

Alternatives:

• grace: Graceful restart & zero downtime deploy for Go servers.
• graceful: Graceful is a Go package enabling graceful shutdown of an http.Handler server.
• manners: A polite Go HTTP server that shuts down gracefully.

Manually

In case you are using Go 1.8 or a later version, you may not need to use those libraries. Consider using http.Server's built-in Shutdown() method for graceful shutdowns. The example below describes its usage, and we've got more examples using gin here.

// +build go1.8

package main

import (
  "context"
  "log"
  "net/http"
  "os"
  "os/signal"
  "syscall"
  "time"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  router.GET("/", func(c *gin.Context) {
    time.Sleep(5 * time.Second)
    c.String(http.StatusOK, "Welcome Gin Server")
  })

  srv := &http.Server{
    Addr:    ":8080",
    Handler: router,
  }

  // Initializing the server in a goroutine so that
  // it won't block the graceful shutdown handling below
  go func() {
    if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
      log.Printf("listen: %s\n", err)
    }
  }()

  // Wait for interrupt signal to gracefully shutdown the server with
  // a timeout of 5 seconds.
  quit := make(chan os.Signal)
  // kill (no param) default send syscall.SIGTERM
  // kill -2 is syscall.SIGINT
  // kill -9 is syscall.SIGKILL but can't be caught, so don't need to add it
  signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
  <-quit
  log.Println("Shutting down server...")

  // The context is used to inform the server it has 5 seconds to finish
  // the request it is currently handling
  ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
  defer cancel()

  if err := srv.Shutdown(ctx); err != nil {
    log.Fatal("Server forced to shutdown:", err)
  }

  log.Println("Server exiting")
}

Build a single binary with templates

You can build a server into a single binary containing templates by using the embed package.

package main

import (
  "embed"
  "html/template"
  "net/http"

  "github.com/gin-gonic/gin"
)

//go:embed assets/* templates/*
var f embed.FS

func main() {
  router := gin.Default()
  templ := template.Must(template.New("").ParseFS(f, "templates/*.tmpl", "templates/foo/*.tmpl"))
  router.SetHTMLTemplate(templ)

  // example: /public/assets/images/example.png
  router.StaticFS("/public", http.FS(f))

  router.GET("/", func(c *gin.Context) {
    c.HTML(http.StatusOK, "index.tmpl", gin.H{
      "title": "Main website",
    })
  })

  router.GET("/foo", func(c *gin.Context) {
    c.HTML(http.StatusOK, "bar.tmpl", gin.H{
      "title": "Foo website",
    })
  })

  router.GET("favicon.ico", func(c *gin.Context) {
    file, _ := f.ReadFile("assets/favicon.ico")
    c.Data(
      http.StatusOK,
      "image/x-icon",
      file,
    )
  })

  router.Run(":8080")
}

See a complete example in the https://github.com/gin-gonic/examples/tree/master/assets-in-binary/example02 directory.

Bind form-data request with custom struct

The follow example using custom struct:

type StructA struct {
    FieldA string `form:"field_a"`
}

type StructB struct {
    NestedStruct StructA
    FieldB string `form:"field_b"`
}

type StructC struct {
    NestedStructPointer *StructA
    FieldC string `form:"field_c"`
}

type StructD struct {
    NestedAnonyStruct struct {
        FieldX string `form:"field_x"`
    }
    FieldD string `form:"field_d"`
}

func GetDataB(c *gin.Context) {
    var b StructB
    c.Bind(&b)
    c.JSON(http.StatusOK, gin.H{
        "a": b.NestedStruct,
        "b": b.FieldB,
    })
}

func GetDataC(c *gin.Context) {
    var b StructC
    c.Bind(&b)
    c.JSON(http.StatusOK, gin.H{
        "a": b.NestedStructPointer,
        "c": b.FieldC,
    })
}

func GetDataD(c *gin.Context) {
    var b StructD
    c.Bind(&b)
    c.JSON(http.StatusOK, gin.H{
        "x": b.NestedAnonyStruct,
        "d": b.FieldD,
    })
}

func main() {
    r := gin.Default()
    r.GET("/getb", GetDataB)
    r.GET("/getc", GetDataC)
    r.GET("/getd", GetDataD)

    r.Run()
}

Using the command curl command result:

$ curl "http://localhost:8080/getb?field_a=hello&field_b=world"
{"a":{"FieldA":"hello"},"b":"world"}
$ curl "http://localhost:8080/getc?field_a=hello&field_c=world"
{"a":{"FieldA":"hello"},"c":"world"}
$ curl "http://localhost:8080/getd?field_x=hello&field_d=world"
{"d":"world","x":{"FieldX":"hello"}}

Try to bind body into different structs

The normal methods for binding request body consumes c.Request.Body and they cannot be called multiple times.

type formA struct {
  Foo string `json:"foo" xml:"foo" binding:"required"`
}

type formB struct {
  Bar string `json:"bar" xml:"bar" binding:"required"`
}

func SomeHandler(c *gin.Context) {
  objA := formA{}
  objB := formB{}
  // This c.ShouldBind consumes c.Request.Body and it cannot be reused.
  if errA := c.ShouldBind(&objA); errA == nil {
    c.String(http.StatusOK, `the body should be formA`)
  // Always an error is occurred by this because c.Request.Body is EOF now.
  } else if errB := c.ShouldBind(&objB); errB == nil {
    c.String(http.StatusOK, `the body should be formB`)
  } else {
    ...
  }
}

For this, you can use c.ShouldBindBodyWith or shortcuts.

• c.ShouldBindBodyWithJSON is a shortcut for c.ShouldBindBodyWith(obj, binding.JSON).
• c.ShouldBindBodyWithXML is a shortcut for c.ShouldBindBodyWith(obj, binding.XML).
• c.ShouldBindBodyWithYAML is a shortcut for c.ShouldBindBodyWith(obj, binding.YAML).
• c.ShouldBindBodyWithTOML is a shortcut for c.ShouldBindBodyWith(obj, binding.TOML).

func SomeHandler(c *gin.Context) {
  objA := formA{}
  objB := formB{}
  // This reads c.Request.Body and stores the result into the context.
  if errA := c.ShouldBindBodyWith(&objA, binding.Form); errA == nil {
    c.String(http.StatusOK, `the body should be formA`)
  // At this time, it reuses body stored in the context.
  } else if errB := c.ShouldBindBodyWith(&objB, binding.JSON); errB == nil {
    c.String(http.StatusOK, `the body should be formB JSON`)
  // And it can accepts other formats
  } else if errB2 := c.ShouldBindBodyWithXML(&objB); errB2 == nil {
    c.String(http.StatusOK, `the body should be formB XML`)
  } else {
    ...
  }
}

1. c.ShouldBindBodyWith stores body into the context before binding. This has a slight impact to performance, so you should not use this method if you are enough to call binding at once.
2. This feature is only needed for some formats -- JSON, XML, MsgPack, ProtoBuf. For other formats, Query, Form, FormPost, FormMultipart, can be called by c.ShouldBind() multiple times without any damage to performance (See #1341).

Bind form-data request with custom struct and custom tag

const (
  customerTag = "url"
  defaultMemory = 32 << 20
)

type customerBinding struct {}

func (customerBinding) Name() string {
  return "form"
}

func (customerBinding) Bind(req *http.Request, obj any) error {
  if err := req.ParseForm(); err != nil {
    return err
  }
  if err := req.ParseMultipartForm(defaultMemory); err != nil {
    if err != http.ErrNotMultipart {
      return err
    }
  }
  if err := binding.MapFormWithTag(obj, req.Form, customerTag); err != nil {
    return err
  }
  return validate(obj)
}

func validate(obj any) error {
  if binding.Validator == nil {
    return nil
  }
  return binding.Validator.ValidateStruct(obj)
}

// Now we can do this!!!
// FormA is an external type that we can't modify it's tag
type FormA struct {
  FieldA string `url:"field_a"`
}

func ListHandler(s *Service) func(ctx *gin.Context) {
  return func(ctx *gin.Context) {
    var urlBinding = customerBinding{}
    var opt FormA
    err := ctx.MustBindWith(&opt, urlBinding)
    if err != nil {
      ...
    }
    ...
  }
}

http2 server push

http.Pusher is supported only go1.8+. See the golang blog for detail information.

package main

import (
  "html/template"
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

var html = template.Must(template.New("https").Parse(`
<html>
<head>
  <title>Https Test</title>
  <script src="/assets/app.js"></script>
</head>
<body>
  <h1 style="color:red;">Welcome, Ginner!</h1>
</body>
</html>
`))

func main() {
  r := gin.Default()
  r.Static("/assets", "./assets")
  r.SetHTMLTemplate(html)

  r.GET("/", func(c *gin.Context) {
    if pusher := c.Writer.Pusher(); pusher != nil {
      // use pusher.Push() to do server push
      if err := pusher.Push("/assets/app.js", nil); err != nil {
        log.Printf("Failed to push: %v", err)
      }
    }
    c.HTML(http.StatusOK, "https", gin.H{
      "status": "success",
    })
  })

  // Listen and Server in https://127.0.0.1:8080
  r.RunTLS(":8080", "./testdata/server.pem", "./testdata/server.key")
}

Define format for the log of routes

The default log of routes is:

[GIN-debug] POST   /foo                      --> main.main.func1 (3 handlers)
[GIN-debug] GET    /bar                      --> main.main.func2 (3 handlers)
[GIN-debug] GET    /status                   --> main.main.func3 (3 handlers)

If you want to log this information in given format (e.g. JSON, key values or something else), then you can define this format with gin.DebugPrintRouteFunc. In the example below, we log all routes with standard log package but you can use another log tools that suits of your needs.

import (
  "log"
  "net/http"

  "github.com/gin-gonic/gin"
)

func main() {
  r := gin.Default()
  gin.DebugPrintRouteFunc = func(httpMethod, absolutePath, handlerName string, nuHandlers int) {
    log.Printf("endpoint %v %v %v %v\n", httpMethod, absolutePath, handlerName, nuHandlers)
  }

  r.POST("/foo", func(c *gin.Context) {
    c.JSON(http.StatusOK, "foo")
  })

  r.GET("/bar", func(c *gin.Context) {
    c.JSON(http.StatusOK, "bar")
  })

  r.GET("/status", func(c *gin.Context) {
    c.JSON(http.StatusOK, "ok")
  })

  // Listen and Server in http://0.0.0.0:8080
  r.Run()
}

Set and get a cookie

import (
  "fmt"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()

  router.GET("/cookie", func(c *gin.Context) {

      cookie, err := c.Cookie("gin_cookie")

      if err != nil {
          cookie = "NotSet"
          c.SetCookie("gin_cookie", "test", 3600, "/", "localhost", false, true)
      }

      fmt.Printf("Cookie value: %s \n", cookie)
  })

  router.Run()
}

Don't trust all proxies

Gin lets you specify which headers to hold the real client IP (if any), as well as specifying which proxies (or direct clients) you trust to specify one of these headers.

Use function SetTrustedProxies() on your gin.Engine to specify network addresses or network CIDRs from where clients which their request headers related to client IP can be trusted. They can be IPv4 addresses, IPv4 CIDRs, IPv6 addresses or IPv6 CIDRs.

Attention: Gin trust all proxies by default if you don't specify a trusted proxy using the function above, this is NOT safe. At the same time, if you don't use any proxy, you can disable this feature by using Engine.SetTrustedProxies(nil), then Context.ClientIP() will return the remote address directly to avoid some unnecessary computation.

import (
  "fmt"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  router.SetTrustedProxies([]string{"192.168.1.2"})

  router.GET("/", func(c *gin.Context) {
    // If the client is 192.168.1.2, use the X-Forwarded-For
    // header to deduce the original client IP from the trust-
    // worthy parts of that header.
    // Otherwise, simply return the direct client IP
    fmt.Printf("ClientIP: %s\n", c.ClientIP())
  })
  router.Run()
}

Notice: If you are using a CDN service, you can set the Engine.TrustedPlatform to skip TrustedProxies check, it has a higher priority than TrustedProxies. Look at the example below:

import (
  "fmt"

  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  // Use predefined header gin.PlatformXXX
  // Google App Engine
  router.TrustedPlatform = gin.PlatformGoogleAppEngine
  // Cloudflare
  router.TrustedPlatform = gin.PlatformCloudflare
  // Fly.io
  router.TrustedPlatform = gin.PlatformFlyIO
  // Or, you can set your own trusted request header. But be sure your CDN
  // prevents users from passing this header! For example, if your CDN puts
  // the client IP in X-CDN-Client-IP:
  router.TrustedPlatform = "X-CDN-Client-IP"

  router.GET("/", func(c *gin.Context) {
    // If you set TrustedPlatform, ClientIP() will resolve the
    // corresponding header and return IP directly
    fmt.Printf("ClientIP: %s\n", c.ClientIP())
  })
  router.Run()
}

Testing

The net/http/httptest package is preferable way for HTTP testing.

package main

import (
  "net/http"

  "github.com/gin-gonic/gin"
)

func setupRouter() *gin.Engine {
  r := gin.Default()
  r.GET("/ping", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
  })
  return r
}

func main() {
  r := setupRouter()
  r.Run(":8080")
}

Test for code example above:

package main

import (
  "net/http"
  "net/http/httptest"
  "testing"

  "github.com/stretchr/testify/assert"
)

func TestPingRoute(t *testing.T) {
  router := setupRouter()

  w := httptest.NewRecorder()
  req, _ := http.NewRequest(http.MethodGet, "/ping", nil)
  router.ServeHTTP(w, req)

  assert.Equal(t, http.StatusOK, w.Code)
  assert.Equal(t, "pong", w.Body.String())
}