Set MKMapview as mainview

MapViewController.swift

import UIKit
import MapKit

class MapViewController: ViewController, MKMapViewDelegate {
  
  var mapView: MKMapView!
  
   override func loadView() {
      // Create a MapView
      mapView = MKMapView()
      
      // set it as *the* view of this view controller
      view = mapView
   }

}