location manager is not on main thread after segue? - ios

Question

I have a serious problem about use location manage and mapview.
I create a app simple show where the location I am now, it runs ok when only one viewcontroller, but after I added a viewController and segue, and after segue first viewController to map viewController, it has some error message:
location manager (0x101f3d870) was created on a dispatch queue executing on a thread other than the main thread
after that, the App crash with this error message :
MKMapView must be initialized on the main thread
But I really move the code into the main thread, and it does ok before I added first viewcontroller and segue!!! The code at below:
import UIKit
import MapKit
import CoreLocation
class Map_ViewController: UIViewController,MKMapViewDelegate,CLLocationManagerDelegate,UISearchBarDelegate {
#IBOutlet weak var mapView: MKMapView!
var cloaction = CLLocationManager()
var span = MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)
var currentLat : Double = 0
var currentLon : Double = 0
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
// Start get the location on viewWillAppear
DispatchQueue.main.async {
self.mapView.delegate = self
self.mapView.showsScale = true
self.mapView.showsPointsOfInterest = true
self.mapView.showsUserLocation = true
self.cloaction.requestAlwaysAuthorization()
self.cloaction.requestWhenInUseAuthorization()
if CLLocationManager.locationServicesEnabled() {
self.cloaction.delegate = self
self.cloaction.desiredAccuracy = kCLLocationAccuracyBest
self.cloaction.startUpdatingLocation()
}
setCenter()
}
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
if let location = locations.last {
mapView.region.center = CLLocationCoordinate2D(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)
mapView.setRegion(mapView.region, animated: false)
}
}
func setCenter() {
let center = CLLocationCoordinate2D(latitude: mapView.userLocation.coordinate.latitude, longitude: mapView.userLocation.coordinate.longitude)
mapView.region.center = center
mapView.region.span = span
mapView.setRegion(mapView.region, animated: true)
}
}
The segue in the main viewController :
override func viewDidLoad() {
super.viewDidLoad()
self.performSegue(withIdentifier: "goToMap", sender: nil)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
print("goToMapViewController")
}