code: func (u URL) Cmp(url URL) int {
  	if u.Scheme == url.Scheme {
  		return strings.Compare(u.Path, url.Path)
  	}
  	return strings.Compare(u.Scheme, url.Scheme)
  }
docs: // Cmp compares x and y and returns:
  //
  //   -1 if x <  y
  //    0 if x == y
  //   +1 if x >  y
  //