how to `go install` from gitea

I'm trying to install a package from a self-hosted gitea instance. I'm trying to get a package running go install gitea.urkob.com/urko/go-root-dir but I'm getting this error

no required module provides package gitea.urkob.com/urko/go-root-dir; to add it:        go get gitea.urkob.com/urko/go-root-dir

Any help would be appreciated to show me how can I configure my go env.

I've set GOPRIVATE="gitea.urkob.com/urko" but it still not working, I don't know if I'm missing something.