add readme.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

README.md

@@ -22,3 +22,37 @@ Import it in your code:
 ```go
 import "github.com/gin-contrib/static"
 ```
+
+### Canonical example:
+
+See the [example](example)
+
+```go
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/gin-contrib/cache"
+	"github.com/gin-contrib/cache/persistence"
+	"gopkg.in/gin-gonic/gin.v1"
+)
+
+func main() {
+	r := gin.Default()
+
+	store := persistence.NewInMemoryStore(time.Second)
+	// Cached Page
+	r.GET("/ping", func(c *gin.Context) {
+		c.String(200, "pong "+fmt.Sprint(time.Now().Unix()))
+	})
+
+	r.GET("/cache_ping", cache.CachePage(store, time.Minute, func(c *gin.Context) {
+		c.String(200, "pong "+fmt.Sprint(time.Now().Unix()))
+	}))
+
+	// Listen and Server in 0.0.0.0:8080
+	r.Run(":8080")
+}
+```