title: Replace pushViewController with segue in MapKit
body: <p>I created app with own MKAnnotation. I have another ViewController and I try send data by segue.
  Now, I have Navigation Controller and working code like this</p>
  
  <pre><code>func mapView(_ mapView: MKMapView, annotationView view: MKAnnotationView, calloutAccessoryControlTapped control: UIControl) {
  
      let annotationView:MyAnnotation = view.annotation as! MyAnnotation
      let storyboard = UIStoryboard(name: "Main", bundle: nil)
      let detailStoryboard = storyboard.instantiateViewController(withIdentifier: "stationDetails") as! DetailViewController
      detailStoryboard.stationTitleText = (annotationView.title)!
      detailStoryboard.bikeRacksText = (annotationView.bike_racks)!
      detailStoryboard.bikesText = (annotationView.bikes)!
      detailStoryboard.freeRacksText = (annotationView.free_racks)!
      detailStoryboard.distanceText = (annotationView.distance)!
      self.navigationController?.pushViewController(detailStoryboard, animated: true)
  }
  </code></pre>
  
  <p>But, I want replace Navigation Controller by segue. 
  I created segue with identifier "pinTouched", and replace last line in my code by</p>
  
  <pre><code>performSegue(withIdentifier: "pinTouched", sender: nil)
  </code></pre>
  
  <p>My perform func look like this</p>
  
  <pre><code>override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
      if (segue.identifier == "pinTouched")
      {
          var detailScreen = segue.destination as! DetailViewController
      }
  }
  </code></pre>
  
  <p>I tried in few ways send this data in this function, but I have only white screen.
  How can I fix it?</p>
  
  <p>Thanks for answer! :)</p>