golang 安装常用工具

配置环境变量 GOPATH，下载后的工具源代码和编译后包会安装到GOPATH的第一个配置路径的src, bin, pkg目录下；配置环境变量 GOPATH/bin；配置环境变量 GIT；分别执行下面命令：

go get -u -v github.com/nsf/gocode
go get -u -v github.com/rogpeppe/godef
go get -u -v github.com/golang/lint/golint
go get -u -v github.com/lukehoban/go-outline
go get -u -v sourcegraph.com/sqs/goreturns
go get -u -v golang.org/x/tools/cmd/gorename
go get -u -v github.com/tpng/gopkgs
go get -u -v github.com/newhook/go-symbols
go get -u -v golang.org/x/tools/cmd/guru

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