1 对于程序中的GitHub包找不到的问题，会报错，只需执行go get -v -u github.com/gorilla/mux 后面跟上找不到的包名
cannot find package "github.com/gorilla/websocket" in any of:
/usr/local/Cellar/go/1.15.2/libexec/src/github.com/gorilla/websocket (from $GOROOT)
/Users/hanhua/go/src/github.com/gorilla/websocket (from $GOPATH)
https://stackoverflow.com/questions/41539909/cannot-find-package-github-com-gorilla-mux-in-any-of