code: func GetMaxEmitAtTimeSinceGPSEpochForDevEUI(db sqlx.Queryer, devEUI lorawan.EUI64) (time.Duration, error) {
  	var timeSinceGPSEpoch time.Duration
  	err := sqlx.Get(db, &timeSinceGPSEpoch, `
  		select
  			coalesce(max(emit_at_time_since_gps_epoch), 0)
  		from
  			device_queue
  		where
  			dev_eui = $1`,
  		devEUI,
  	)
  	if err != nil {
  		return 0, handlePSQLError(err, "select error")
  	}
  
  	return timeSinceGPSEpoch, nil
  }
docs: // GetMaxEmitAtTimeSinceGPSEpochForDevEUI returns the maximum / last GPS
  // epoch scheduling timestamp for the given DevEUI.