use go1.11 with go mod

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

@@ -1,33 +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 (
-	"fmt"
-	"io"
-	"net/http"
-)
-
-type String struct {
-	Format string
-	Data   []interface{}
-}
-
-var plainContentType = []string{"text/plain; charset=utf-8"}
-
-func (r String) Render(w http.ResponseWriter) error {
-	WriteString(w, r.Format, r.Data)
-	return nil
-}
-
-func WriteString(w http.ResponseWriter, format string, data []interface{}) {
-	writeContentType(w, plainContentType)
-
-	if len(data) > 0 {
-		fmt.Fprintf(w, format, data...)
-	} else {
-		io.WriteString(w, format)
-	}
-}