code: func (dp *DHCPPool) GetMACIndex(index uint64) (uint64, string, error) {
  	dp.lock.Lock()
  	defer dp.lock.Unlock()
  
  	if !dp.IndexInPool(index) {
  		return index, FreeMac, errors.New("The index is not part of the pool")
  	}
  
  	if _, free := dp.free[index]; free {
  		return index, FreeMac, nil
  	} else {
  		return index, dp.mac[index], nil
  	}
  }
docs: // Check if the IP is free at the index