Update README.md add godev

README.md

@@ -2,6 +2,7 @@
 
 [![Build Status](https://travis-ci.org/apache/dubbo-go.svg?branch=master)](https://travis-ci.org/apache/dubbo-go)
 [![codecov](https://codecov.io/gh/apache/dubbo-go/branch/master/graph/badge.svg)](https://codecov.io/gh/apache/dubbo-go)
+[![go.dev reference](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat-square)](https://pkg.go.dev/github.com/apache/dubbo-go?tab=doc)
 
 ---
 Apache Dubbo Go Implementation.