Swift 3 showing Firebase all users profile picture on map as annotation - swift

Question

I want to show user's profile pictures on map. I am storing datas on Firebase as longitude, latitude , photo as url on Firebase. Now, I am getting datas for all users on console. But I could not show these datas as annotation. Profile pictures will show on map according to longitude and latitude. How can I do this. I searched lots of websites and lots of tutorials. I could not find anything. All of shows that adding one picture on map as annotation. I want to do this for all users.`
class HomeTest: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate {
#IBOutlet weak var mapView: MKMapView!
var ref = Database.database().reference()
var storageRef = Storage.storage().reference()
let manager = CLLocationManager()
var users = [User] ()
override func viewDidLoad() {
super.viewDidLoad()
self.mapView.delegate = self
manager.delegate = self
manager.desiredAccuracy = kCLLocationAccuracyBest
manager.requestWhenInUseAuthorization()
manager.startUpdatingLocation()
fetchUser()
}
func fetchUser() {
Database.database().reference().child("locations").observe(.childAdded, with: {(snapshot) in
if let dictionary = snapshot.value as? [String: AnyObject] {
let user = User()
user.latitude = dictionary["latitude"] as! Float
user.longitude = dictionary["longitude"] as! Float
user.photo = dictionary["photo"] as! String
//user.username = dictionary["username"] as! String
print(user.latitude, user.longitude, user.photo)
self.users.append(user)
DispatchQueue.main.async(execute: {
// ???
})
}
} , withCancel: nil)
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let location = locations [0]
let myLocation: CLLocationCoordinate2D = CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude)
let span:MKCoordinateSpan = MKCoordinateSpanMake(0.020,0.020)
let region:MKCoordinateRegion = MKCoordinateRegionMake(myLocation,span)
self.mapView.setRegion(region, animated: true)
self.mapView.isZoomEnabled = true
self.mapView.isScrollEnabled = true
self.mapView.showsUserLocation = true
}
}