How to track user location in the background swift

I am trying to track the user location in background I have try using when In us with and without always , but every time I minimise the app the location icon disappear I have read in a tutorial it should show blue bar but I am not getting that bar I have also check the background mode for updating the location

  map.showsUserLocation = true
    locationManager.delegate = self
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.requestWhenInUseAuthorization()
    locationManager.requestAlwaysAuthorization()
    locationManager.startUpdatingLocation()
    // Do any additional setup after loading the view, typically from a nib.
    alwaysAuthorization()
}

func alwaysAuthorization(){
    if CLLocationManager.locationServicesEnabled() && CLLocationManager.authorizationStatus() == .authorizedWhenInUse {
        locationManager.requestAlwaysAuthorization()
    }
}


func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    let location = locations.last
    let region  = MKCoordinateRegion(center: CLLocationCoordinate2D(latitude: location!.coordinate.latitude, longitude: location!.coordinate.longitude), span: MKCoordinateSpan (latitudeDelta: 0.2, longitudeDelta: 0.2))
    self.map.region = region
    print("location \(location!.coordinate.latitude) and \(location!.coordinate.longitude)")
}

this what I was looking for

        locationManager.allowsBackgroundLocationUpdates = true