Merge pull request #314 from LinuxSuRen/contribution-go-proxy

Add golang module proxy setting documentation

CONTRIBUTING.md

 Welcome! Any kinds of contributions are very welcome. Please go through our contribution
 guide before you create a Pull Request for `jcli`.
 
+## Golang Environment
+
+Go module proxy setting can speed the download of the dependencies:
+
+`export GOPROXY=https://mirrors.aliyun.com/goproxy/`
+
 ## CLI
 
 `jcli` is a command line interface. So a CLI framework is super important for us. Thanks to