Cannot assign locationManager() function to DispatchQueue.main.async { * } - ios

Question

I am getting an error while trying to assign function locationManager() in the DispatchQueue.main.async {}, ill provide whole code and specific pic of error for more clarity --> Here
I got most of the code from SeanAllen on yt since I am new to swift and learning everyday so this code isn't my logic, and the function fetchAndReloadData() is my functionalists I created to get the lat and long from the API assigning to the correct car id since it will track Vehicles on map (car tracking app)
class MapViewController: UIViewController, MKMapViewDelegate {
var globalVechicle = [Vehicles]()
var id = "6438367CC43848B497FE4604AF465D6A"
let locationManager = CLLocationManager()
let regionInMeters: Double = 10000
#IBOutlet weak var mapView: MKMapView!
#IBAction func changeMapType(_ sender: UISegmentedControl) {
if sender.selectedSegmentIndex == 0 {
mapView.mapType = .standard
}else {
mapView.mapType = .satellite
}
}
#IBAction func closeButton(_ sender: Any) {
dismiss(animated: true, completion: nil)
}
override func viewDidLoad() {
super.viewDidLoad()
checkLocationServices()
}
func setupLocationManager() {
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyBest
}
func centerViewOnUserLocation() {
if let location = locationManager.location?.coordinate {
let region = MKCoordinateRegion.init(center: location, latitudinalMeters: regionInMeters, longitudinalMeters: regionInMeters)
mapView.setRegion(region, animated: true)
}
}
func checkLocationServices() {
if CLLocationManager.locationServicesEnabled() {
setupLocationManager()
checkLocationAuthorization()
} else {
// show alert they have to turn it on
}
}
func checkLocationAuthorization() {
switch CLLocationManager.authorizationStatus() {
case .authorizedWhenInUse:
mapView.showsUserLocation = true
centerViewOnUserLocation()
fetchAndReloadData()
locationManager.startUpdatingLocation()
break
case .denied:
// show alert instructing them how to turn on the permissions
break
case .notDetermined:
locationManager.requestWhenInUseAuthorization()
case .restricted:
// Show an alert letting them know what's up
break
case .authorizedAlways:
break
#unknown default:
print("Error")
}
}
}
extension MapViewController: CLLocationManagerDelegate {
func fetchAndReloadData(){
APICaller.shared.getVehicles(for: id) {[weak self] (result) in
guard let self = self else { return }
switch result {
case .success(let vehicle):
self.globalVechicle = vehicle
DispatchQueue.main.async {
self.locationManager()
}
case .failure(let error):
print(error)
}
}
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
guard let lattitude = globalVechicle[0].Latitude ,let longitude = globalVechicle[0].Longitude else { return }
let carLocation = CLLocationCoordinate2D(latitude: lattitude , longitude: longitude)
let region = MKCoordinateRegion.init(center: carLocation, latitudinalMeters: regionInMeters, longitudinalMeters: regionInMeters)
mapView.setRegion(region, animated: true)
mapView.delegate = self
}
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
checkLocationAuthorization()
}
}