It is part of POSIX: https://github.com/golang/go/issues/36822#issuecomment-579381348 https://github.com/golang/go/issues/36822#issuecomment-57938... Also RFC

It is part of POSIX: https://github.com/golang/go/issues/36822#issuecomment-579381348 https://github.com/golang/go/issues/36822#issuecomment-57938... Also RFC 3986.