add upload file example.

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

examples/upload-file/single/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+
+	"github.com/gin-gonic/gin"
+)
+
+func main() {
+	router := gin.Default()
+	router.Static("/", "./public")
+	router.POST("/upload", func(c *gin.Context) {
+		name := c.PostForm("name")
+		email := c.PostForm("email")
+
+		// Source
+		file, _ := c.FormFile("file")
+		src, _ := file.Open()
+		defer src.Close()
+
+		// Destination
+		dst, _ := os.Create(file.Filename)
+		defer dst.Close()
+
+		// Copy
+		io.Copy(dst, src)
+
+		c.String(http.StatusOK, fmt.Sprintf("File %s uploaded successfully with fields name=%s and email=%s.", file.Filename, name, email))
+	})
+	router.Run(":8080")
+}