How to animate a polyline in a map (iOS)?

Hi! I',m developing an application in Xamarin Forms and based on the examples of Xamarin Forms i did this:

https://developer.xamarin.com/recipes/cross-platform/xamarin-forms/maps/map-overlay/polyline/

And I modify the CustomMapRender.cs class in android project:

using System.Collections.Generic;
using Android.Gms.Maps;
using Android.Gms.Maps.Model;
using MapOverlay;
using MapOverlay.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Maps;
using Xamarin.Forms.Maps.Android;
using System.Threading.Tasks;

[assembly:ExportRenderer (typeof(CustomMap), typeof(CustomMapRenderer))]
namespace MapOverlay.Droid
{
public class CustomMapRenderer : MapRenderer, IOnMapReadyCallback
{
GoogleMap map;
List routeCoordinates;

    protected override void OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs<View> e)
    {
        base.OnElementChanged (e);

        if (e.OldElement != null) {
            // Unsubscribe
        }

        if (e.NewElement != null) {
            var formsMap = (CustomMap)e.NewElement;
            routeCoordinates = formsMap.RouteCoordinates;

            ((MapView)Control).GetMapAsync (this);
        }
    }

    public void OnMapReady (GoogleMap googleMap)
    {
        map = googleMap;

        var polylineOptions = new PolylineOptions ();
        polylineOptions.InvokeColor (0x66FF0000);

        foreach (var position in routeCoordinates) {
            polylineOptions.Add (new LatLng (position.Latitude, position.Longitude));
            await Task.Delay(30);
        }

        map.AddPolyline (polylineOptions);
    }
}

}

In Android, the Delay in the foreach animate the polyline, and the idea is that animating the polyline you can see the direction of the route.

But, I want to do the same in iOS project, but I don't know how to implement the same idea. I have the code that show the route, is the same class, CustomMapRenderer.cs

namespace MapOverlay.iOS
{
public class CustomMapRenderer : MapRenderer
{
MKPolylineRenderer polylineRenderer;

    protected override void OnElementChanged (ElementChangedEventArgs<View> e)
    {
        base.OnElementChanged (e);

        if (e.OldElement != null) {
            var nativeMap = Control as MKMapView;
            nativeMap.OverlayRenderer = null;
        }

        if (e.NewElement != null) {
            var formsMap = (CustomMap)e.NewElement;
            var nativeMap = Control as MKMapView;

            nativeMap.OverlayRenderer = GetOverlayRenderer;

            CLLocationCoordinate2D[] coords = new CLLocationCoordinate2D[formsMap.RouteCoordinates.Count];

            int index = 0;
            foreach (var position in formsMap.RouteCoordinates) {
                coords [index] = new CLLocationCoordinate2D (position.Latitude, position.Longitude);
                index++;
            }

            var routeOverlay = MKPolyline.FromCoordinates (coords);
            nativeMap.AddOverlay (routeOverlay);
        }
    }

    MKOverlayRenderer GetOverlayRenderer (MKMapView mapView, IMKOverlay overlay)
    {
        if (polylineRenderer == null) {
            polylineRenderer = new MKPolylineRenderer (overlay as MKPolyline);
            polylineRenderer.FillColor = UIColor.Blue;
            polylineRenderer.StrokeColor = UIColor.Red;
            polylineRenderer.LineWidth = 3;
            polylineRenderer.Alpha = 0.4f;
        }
        return polylineRenderer;
    }
}

}

Any idea of how I can do this?

Thank you and regards from Mexico.