测试环境
$ go version
go version go1.14.3 darwin/amd64
$ sw_vers
ProductName: Mac OS X
ProductVersion: 10.14.6
BuildVersion: 18G4032安装Go后，打开VS Code，按照提示安装了微软官方的GO插件。但在安装go tools时，出现了下面的一大堆错误。
go.toolsGopath setting is not set. Using GOPATH /Users/l2m2/go
Installing 17 tools at /Users/l2m2/go/bin in module mode.
gocode
gopkgs
go-outline
go-symbols
guru
gorename
gotests
gomodifytags
impl
fillstruct
goplay
godoctor
dlv
gocode-gomod
godef
goimports
golint
Installing github.com/mdempsky/gocode FAILED
Installing github.com/uudashr/gopkgs/v2/cmd/gopkgs FAILED
Installing github.com/ramya-rao-a/go-outline FAILED
Installing github.com/acroca/go-symbols FAILED
Installing golang.org/x/tools/cmd/guru FAILED
Installing golang.org/x/tools/cmd/gorename FAILED
Installing github.com/cweill/gotests/... FAILED
Installing github.com/fatih/gomodifytags FAILED
Installing github.com/josharian/impl FAILED
Installing github.com/davidrjenni/reftools/cmd/fillstruct FAILED
Installing github.com/haya14busa/goplay/cmd/goplay FAILED
Installing github.com/godoctor/godoctor FAILED
Installing github.com/go-delve/delve/cmd/dlv FAILED
Installing github.com/stamblerre/gocode FAILED
Installing github.com/rogpeppe/godef FAILED
Installing golang.org/x/tools/cmd/goimports FAILED
Installing golang.org/x/lint/golint FAILED
17 tools failed to install.
gocode:
Error: Command failed: /usr/local/go/bin/go get -v github.com/mdempsky/gocode
go get github.com/mdempsky/gocode: module github.com/mdempsky/gocode: Get "https://proxy.golang.org/github.com/mdempsky/gocode/@v/list": dial tcp 172.217.160.113:443: i/o timeout
go get github.com/mdempsky/gocode: module github.com/mdempsky/gocode: Get "https://proxy.golang.org/github.com/mdempsky/gocode/@v/list": dial tcp 172.217.160.113:443: i/o timeout解决方案
设置代理：
go env -w GO111MODULE=on
go env -w GOPROXY=https://proxy.golang.com.cn,direct设置完成后重启VS Code，按照提示安装即可。
在go 1.13及以后的版本中，如果环境变量GOPROXY未设置
在Go 1.13及以上版本中，默认的GO111MODULE设置是"auto"
References
https://l2m2.top/2020/05/26/2020-05-26-fix-golang-tools-failed-on-vscode/
