use go1.11 with go mod

vendor/github.com/gin-gonic/gin/binding/protobuf.go

@@ -1,35 +0,0 @@
-// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
-// Use of this source code is governed by a MIT style
-// license that can be found in the LICENSE file.
-
-package binding
-
-import (
-	"github.com/golang/protobuf/proto"
-
-	"io/ioutil"
-	"net/http"
-)
-
-type protobufBinding struct{}
-
-func (protobufBinding) Name() string {
-	return "protobuf"
-}
-
-func (protobufBinding) Bind(req *http.Request, obj interface{}) error {
-
-	buf, err := ioutil.ReadAll(req.Body)
-	if err != nil {
-		return err
-	}
-
-	if err = proto.Unmarshal(buf, obj.(proto.Message)); err != nil {
-		return err
-	}
-
-	//Here it's same to return validate(obj), but util now we cann't add `binding:""` to the struct
-	//which automatically generate by gen-proto
-	return nil
-	//return validate(obj)
-}