code: func HandleDownlinkTXAcks(wg *sync.WaitGroup) {
  	for downlinkTXAck := range gwbackend.Backend().DownlinkTXAckChan() {
  		go func(downlinkTXAck gw.DownlinkTXAck) {
  			wg.Add(1)
  			defer wg.Done()
  			if err := ack.HandleDownlinkTXAck(downlinkTXAck); err != nil {
  				log.WithFields(log.Fields{
  					"gateway_id": hex.EncodeToString(downlinkTXAck.GatewayId),
  					"token":      downlinkTXAck.Token,
  				}).WithError(err).Error("handle downlink tx ack error")
  			}
  
  		}(downlinkTXAck)
  	}
  }
docs: // HandleDownlinkTXAcks consumes received downlink tx acknowledgements from
  // the gateway.