use go1.11 with go mod

vendor/github.com/gin-gonic/gin/render/yaml.go

@@ -1,29 +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 render
-
-import (
-	"net/http"
-
-	"gopkg.in/yaml.v2"
-)
-
-type YAML struct {
-	Data interface{}
-}
-
-var yamlContentType = []string{"application/x-yaml; charset=utf-8"}
-
-func (r YAML) Render(w http.ResponseWriter) error {
-	writeContentType(w, yamlContentType)
-
-	bytes, err := yaml.Marshal(r.Data)
-	if err != nil {
-		return err
-	}
-
-	w.Write(bytes)
-	return nil
-}