feat(context): add SaveUploadedFile func. (#1022)

* feat(context): add SaveUploadedFile func.

* feat(context): update multiple upload examples.

* style(example): fix gofmt

* fix(example): add missing return

context.go

@@ -13,6 +13,7 @@ import (
 	"net"
 	"net/http"
 	"net/url"
+	"os"
 	"strings"
 	"time"
 
@@ -431,6 +432,24 @@ func (c *Context) MultipartForm() (*multipart.Form, error) {
 	return c.Request.MultipartForm, err
 }
 
+// SaveUploadedFile uploads the form file to specific dst.
+func (c *Context) SaveUploadedFile(file *multipart.FileHeader, dst string) error {
+	src, err := file.Open()
+	if err != nil {
+		return err
+	}
+	defer src.Close()
+
+	out, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	io.Copy(out, src)
+	return nil
+}
+
 // Bind checks the Content-Type to select a binding engine automatically,
 // Depending the "Content-Type" header different bindings are used:
 //     "application/json" --> JSON binding