firebase data not updating Map using mapkit annotation

Question

i have a swift code of mapkit and array of annotations but when i tried to fetch data from firebase and append its to annotation the ui not updating,i need to fetch annotations from firebase and display as annotations i mapkit

import Foundation
import MapKit
import Firebase

class EventManagerVM:Identifiable,ObservableObject{
    var id =  UUID()
    @Published var eventName:String = ""
    @Published var eventType:String = ""
    @Published var annotations =  [
        MKPointAnnotation(
            __coordinate: CLLocationCoordinate2D(latitude: 37.335480, longitude: -122.009270),
            title: "Apple Campus",
            subtitle: "Cupertino, CA"
        )
    ]
    
    func fetchEvents(){
        let db = Firestore.firestore()
        db.collection("events").getDocuments { [self] (querySnapshot, error) in
            if let error = error {
                print("Error getting documents: \(error)")
            } else {
                for document in querySnapshot!.documents {
                    let event = Event(name: document.data()["name"] as? String ?? "",
                                      subtitle: document.data()["subtitle"] as? String ?? "",
                                      latitude: document.data()["latitude"] as? Double ?? 0.0,
                                      longitude: document.data()["longitude"] as? Double ?? 0.0)
                    
                    let annotation = MKPointAnnotation()
                    annotation.title = event.name
                    annotation.subtitle = event.subtitle
                    annotation.coordinate = CLLocationCoordinate2D(latitude: event.latitude, longitude: event.longitude)
                    self.annotations.append(annotation)
                    
                    print(annotation)
                  
                }
                print("annotations count")
                print(self.annotations.count)
               
            }
        }
    }
    
}