document jsonp on the README

README.md

@@ -861,6 +861,28 @@ func main() {
 	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.
+
+```go
+func main() {
+	r := gin.Default()
+
+	r.GET("/JSONP?callback=x", func(c *gin.Context) {
+		data := map[string]interface{}{
+			"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")
+}
+```
 
 ### Serving static files