Fix "go get" error "invalid char ':'" when using custom-port.

Korean: https://jsty.tistory.com/334

 We are running gitlab on a non-standard port.

A problem occurred recently when I tried to use the go package through the gitlab repository.

$ go get https://gitlab.company.com:1234/group/pkg-name

go: malformed module path "https:/gitlab.company.com:1234/group/pkg-name": invalid char ':'

Related issues:
- https://github.com/golang/go/issues/26912
- https://stackoverflow.com/questions/60445266/not-able-to-get-private-go-module-while-having-port-number-in-url

I developed a simple service to solve this.
It simply generates metadata to find the actual repository.

See https://github.com/jc-lab/go-pkg-meta-proxy/