code: func (a *Airport) newArrival() error {
  	priority := atomic.AddUint32(&a.priority, 1)
  	flightInfo := &flight.Info{
  		Airline:  a.airlines[rand.Int()%len(a.airlines)],
  		Number:   rand.Uint32()%99 + 1,
  		Priority: priority,
  	}
  	var exists bool
  	flightID := fmt.Sprintf(flightIDFormat, flightInfo.Airline, flightInfo.Number)
  
  	a.Lock()
  	// make sure that the generated flight does not exist yet and "show" it on the flight radar
  	if _, exists = a.flightRadar[flightID]; !exists {
  		a.flightRadar[flightID] = struct{}{}
  		if err := a.arrivalBroker.Put(flightID, flightInfo); err != nil {
  			return errors.Errorf("Arrival %s failed: %v", flightID, err)
  		}
  	}
  	a.Unlock()
  
  	return nil
  }
docs: // Generate new arrival for one of the airlines with some number (everything is chosen randomly)