https://goproxy.io是一个国内的代理
执行

go env -w GO111MODULE=on
go env -w GOPROXY=https://goproxy.io,direct

关闭vscode重新打开,再次点击install all

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成功安装

开启go mod 代理后也可以手动安装

go get -u -v github.com/mdempsky/gocode
go get -u -v github.com/uudashr/gopkgs/v2/cmd/gopkgs
go get -u -v github.com/ramya-rao-a/go-outline
go get -u -v github.com/acroca/go-symbols
go get -u -v golang.org/x/tools/cmd/guru
go get -u -v golang.org/x/tools/cmd/gorename
go get -u -v github.com/cweill/gotests/...
go get -u -v github.com/fatih/gomodifytags
go get -u -v github.com/josharian/impl
go get -u -v github.com/davidrjenni/reftools/cmd/fillstruct
go get -u -v github.com/haya14busa/goplay/cmd/goplay
go get -u -v github.com/godoctor/godoctor
go get -u -v github.com/go-delve/delve/cmd/dlv
go get -u -v github.com/stamblerre/gocode
go get -u -v github.com/rogpeppe/godef
go get -u -v github.com/sqs/goreturns
go get -u -v golang.org/x/lint/golint

如图
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