code: func (s *Server) ListenAndServeUNIX(addr string, mode os.FileMode) error {
  	if err := os.Remove(addr); err != nil && !os.IsNotExist(err) {
  		return fmt.Errorf("unexpected error when trying to remove unix socket file %q: %s", addr, err)
  	}
  	ln, err := net.Listen("unix", addr)
  	if err != nil {
  		return err
  	}
  	if err = os.Chmod(addr, mode); err != nil {
  		return fmt.Errorf("cannot chmod %#o for %q: %s", mode, addr, err)
  	}
  	return s.Serve(ln)
  }
docs: // ListenAndServeUNIX serves HTTP requests from the given UNIX addr.
  //
  // The function deletes existing file at addr before starting serving.
  //
  // The server sets the given file mode for the UNIX addr.