Google Map marker doesnt work

I`m trying to put marker on my current location, I follow the instructions here on putting marker but idk why I my marker does not show. Here is my code


import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { Geolocation } from '@ionic-native/geolocation';
import {
  GoogleMaps,
  GoogleMap,
  GoogleMapsEvent,
  GoogleMapOptions,
  // CameraPosition,
  // MarkerOptions,
  Marker
} from '@ionic-native/google-maps';
@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  map: GoogleMap;
  public longitude:any;
  public latitude:any;
  constructor(
    public navCtrl: NavController,
    private geolocation: Geolocation) {

  }
  ionViewDidLoad() {
  }
  getLocation(){
    alert("Pressed please wait");
    this.geolocation.getCurrentPosition().then((resp) => {
      alert("longitude =>"+resp.coords.latitude+" latitude=>"+resp.coords.latitude);
      this.longitude = resp.coords.latitude;
      this.latitude = resp.coords.latitude;
      let mapOptions: GoogleMapOptions = {
        camera: {
           target: {
             lat: resp.coords.latitude,
             lng: resp.coords.longitude
           },
           zoom: 18,
           tilt: 30
         }
      };
     this.map = GoogleMaps.create('map_canvas',mapOptions);
    }).catch((error) => {
      alert('Error getting location');
    });
  }
  mapMarker(){
    alert('adding marker');
    this.map.addMarker({
      icon: 'red',
      animation: 'DROP',
      position: {
        lat: this.latitude,
        lng: this.longitude
      },
      title: "My position"
    }).then((marker: Marker) =>{

      marker.showInfoWindow();
    });
  }

HTML file

  <button ion-button (click)="mapMarker()">
    <ion-icon name="street-view"></ion-icon>
  </button>
  <ion-fab top right >
  <button ion-fab color="primary">Share</button>
    <ion-fab-list side="left">
      <button ion-fab (click)="getLocation()">
        <ion-icon name="location"></ion-icon>
      </button>
    </ion-fab-list>
  </ion-fab>
  <div id="map_canvas"></div>

I dont have problem in showing the google map, only problem is marker. Any idea why? Thanks

Edit => btw I will click a button in order to show the marker