code: func pprintAddr(listeners []net.Listener) []byte {
  	var out bytes.Buffer
  	for i, l := range listeners {
  		if i != 0 {
  			fmt.Fprint(&out, ", ")
  		}
  		fmt.Fprint(&out, l.Addr())
  	}
  	return out.Bytes()
  }
docs: // Used for pretty printing addresses.