go mod
https://github.com/gomods/athens https://goproxy.cn
https://blog.golang.org/modules2019 https://blog.golang.org/using-go-modules https://blog.golang.org/migrating-to-go-modules https://blog.golang.org/module-mirror-launch https://blog.golang.org/publishing-go-modules https://blog.golang.org/v2-go-modules https://blog.golang.org/module-compatibility