#Gin Web Framework

Gin is a web framework written in Golang. It features a martini-like API with much better performance, up to 40 times faster. If you need performance and good productivity, you will love Gin.

##Gin is new, will it be supported?

Yes, Gin is an internal project of my upcoming startup. We developed it and we are going to continue using and improve it.

##Roadmap for v0.2

• Performance improments, reduce allocation and garbage collection overhead
• Fix bugs
• Ask our designer for a cool logo
• Add tons of unit tests and benchmarks
• Improve logging system
• Improve JSON/XML validation using bindings
• Improve XML support
• Improve documentation
• Add more cool middlewares, for example redis catching (this also helps developers to understand the framework)
• Continuous integration

Start using it

Obviously, you need to have Git and Go! already installed to run Gin.
Run this in your terminal

go get github.com/gin-gonic/gin

Then import it in your Go! code:

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

##API Examples

Create most basic PING/PONG HTTP endpoint

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

func main() {
    r := gin.Default()
    r.GET("/ping", func(c *gin.Context){
        c.String(200, "pong")
    })
    
    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

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

func main() {
    // Creates a gin router + logger and recovery (crash-free) middlewares
    r := gin.Default()
    
    r.GET("/someGet", getting)
    r.POST("/somePost", posting)
    r.PUT("/somePut", putting)
    r.DELETE("/someDelete", deleting)
    r.PATCH("/somePatch", patching)
    r.HEAD("/someHead", head)
    r.OPTIONS("/someOptions", options)

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

Parameters in path

func main() {
    r := gin.Default()
    
    r.GET("/user/:name", func(c *gin.Context) {
        name := c.Params.ByName("name")
        message := "Hello "+name
        c.String(200, message)
    })

    r.GET("/user/:name/:action", func(c *gin.Context) {
        name := c.Params.ByName("name")
        action := c.Params.ByName("action")
        message := name + " is " + action
        c.String(200, message)
    })

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

Grouping routes

func main() {
    r := gin.Default()
    
    // Simple group: v1
    v1 := r.Group("/v1")
    {
        v1.POST("/login", loginEndpoint)
        v1.POST("/submit", submitEndpoint)
        v1.POST("/read", readEndpoint)
    }
    
    // Simple group: v2
    v2 := r.Group("/v2")
    {
        v2.POST("/login", loginEndpoint)
        v2.POST("/submit", submitEndpoint)
        v2.POST("/read", readEndpoint)
    }

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

Blank Gin without middlewares by default

Use

r := gin.New()

instead of

r := gin.Default()

Using middlewares

func main() {
    // Creates a router without any middleware by default
    r := gin.New()
    
    // Global middlewares
    r.Use(gin.Logger())
    r.Use(gin.Recovery())
    
    // Per route middlewares, you can add as many as you desire.
    r.GET("/benchmark", MyBenchLogger(), benchEndpoint)

    // Authorization group
    // authorized := r.Group("/", AuthRequired())
    // exactly the same than:
    authorized := r.Group("/")
    // per group middlewares! 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")
        testing.GET("/analytics", analyticsEndpoint)
    }
   
    // Listen and server on 0.0.0.0:8080
    r.Run(":8080")
}

JSON parsing and validation

type LoginJSON struct {
    User     string `json:"user" binding:"required"`
    Password string `json:"password" binding:"required"`
}

func main() {
    r := gin.Default()
    
    r.POST("/login", func(c *gin.Context) {
        var json LoginJSON
        
        // If EnsureBody returns false, it will write automatically the error
        // in the HTTP stream and return a 400 error. If you want custom error 
        // handling you should use: c.ParseBody(interface{}) error
        if c.EnsureBody(&json) {
            if json.User=="manu" && json.Password=="123" {
                c.JSON(200, gin.H{"status": "you are logged in"})
            }else{
                c.JSON(401, gin.H{"status": "unauthorized"})
            }
        }
    })

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

XML, and JSON rendering

func main() {
    r := gin.Default()
    
    // gin.H is a shortcup for map[string]interface{}
    r.GET("/someJSON", func(c *gin.Context) {
        c.JSON(200, gin.H{"message": "hey", "status": 200})
    })
    
    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(200, msg)
    })
    
    r.GET("/someXML", func(c *gin.Context) {
        c.XML(200, gin.H{"message": "hey", "status": 200})
    })

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

####HTML rendering

Using LoadHTMLTemplates()

func main() {
    r := gin.Default()
    r.LoadHTMLTemplates("templates/*")
    r.GET("/index", func(c *gin.Context) {
        obj := gin.H{"title": "Main website"}
        c.HTML(200, "index.tmpl", obj)
    })

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

You can also use your own html template render

import "html/template"
func main() {
    r := gin.Default()
    html := template.Must(template.ParseFiles("file1", "file2"))
    r.HTMLTemplates = html

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

Custom Middlewares

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 := r.Get("example").(string)
        
        // it would print: "12345"
        log.Println(example)
    })

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

Using BasicAuth() middleware

// similate 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 setted by the BasicAuth middleware
		user := c.Get(gin.AuthUserKey).(string)
		if secret, ok := secrets[user]; ok {
			c.JSON(200, gin.H{"user": user, "secret": secret})
		} else {
			c.JSON(200, gin.H{"user": user, "secret": "NO SECRET :("})
		}
	})

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

Goroutines inside a middleware

When starting 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
		c_cp := c.Copy()
		go func() {
			// simulate a long task with time.Sleep(). 5 seconds
			time.Sleep(5 * time.Second)

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

    // Listen and server 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()
}