code: func addrsUnique(inuse map[string]string, name string, addrs []net.Addr) error {
  	for _, a := range addrs {
  		if err := addrUnique(inuse, name, a); err != nil {
  			return err
  		}
  	}
  	return nil
  }
docs: // addrsUnique checks if any of the give addresses is already in use for
  // another protocol.