code: func (bl *blackList) genKey(ip string, port int) string {
  	key := ip
  	if port >= 0 {
  		key = genAddress(ip, port)
  	}
  	return key
  }
docs: // genKey returns a key. If port is less than 0, the key wil be ip. Ohterwise
  // it will be `ip:port` format.