我会做一个小小的修改，因为最好的做法是要么全部异步，要么全部不异步。当你试图从一个非异步方法返回一个异步方法的结果时，你可能会遇到死锁的问题。另外，因为你在调用GetPosition方法时没有使用await关键字，所以你得到的是一个任务，但不检查操作何时完成，我建议您稍微修改代码。

public interface ICurrentLocation {
    Task<MyLocation> GetCurrentLocation();
}

public async Task<MyLocation> GetCurrentLocation()
{
    var position = await GetPosition();
    return new MyLocation()
    {
        Latitude = position.Latitude,
        Longitude = position.Longitude
    };
}

async Task<Location> GetPosition()
{
    try
    {
          locator = new Geolocator(this) { DesiredAccuracy = 50 };
          if (locator.IsListening != true)
                locator.StartListening(minTime: 1000, minDistance: 0);

          return await locator.GetPositionAsync(timeout: 20000);

    }
    catch (Exception e)
    {
        Log.Debug("GeolocatorError", e.ToString());
    }
}

You aren't waiting for the position function to finish. Many different options and keeping it async is the best one but if you want it synchronous then try this blocking call:

void GetPosition()
   {
       try
       {
             locator = new Geolocator(this) { DesiredAccuracy = 50 };
             if (locator.IsListening != true)
                   locator.StartListening(minTime: 1000, minDistance: 0);

             position = locator.GetPositionAsync(timeout: 20000).Result;

       }
       catch (Exception e)
       {
           Log.Debug("GeolocatorError", e.ToString());
       }
   }

I also recommend taking a look at Xamarin.Forms.Labs as it already has abstracted GPS service and working sample that is functional for all 3 platforms:
https://github.com/XForms/Xamarin-Forms-Labs

请尝试在命名空间上方加入组件，并等候GetPosition方法。
请看这张图片：http://developer.xamarin.com/guides/cross-platform/xamarin-forms/dependency-service/Images/solution.png

我开发了一个应用程序，在获得GPS定位（ALHAMDULILAH）的工作很好。我相信下面的代码将是很大的帮助。
然后，您可以根据自己的喜好编辑SubmitGPSLocation函数。
我希望这对你有帮助...

public async Task Run(CancellationToken token)
    {
        await Task.Run(async () =>
        {
            if (GPSService.Instance.IsListening)
            {
                GPSService.Instance.StopListening();
            }

            GPSService.Instance.StartListening(2500, 50, true); 
            GPSService.Instance.PositionChanged += Instance_PositionChanged;

            System.Diagnostics.Debug.WriteLine(getRunningStateLocationService());

            while (getRunningStateLocationService())
            {
                token.ThrowIfCancellationRequested();                   
                await Task.Delay(500).ConfigureAwait(true);
            }

            GPSService.Instance.StopListening();
          
            //await CrossGeolocator.Current.StopListeningAsync().ConfigureAwait(true);
            GPSService.Instance.PositionChanged -= Instance_PositionChanged;

            return;
        }, token).ConfigureAwait(false);
    }

    private void Instance_PositionChanged(object sender, PositionEventArgs e)
    {
        try
        {
            isEvenCount = !isEvenCount;

            if (e.Position != null)
            { 
                var message = new LocationMessage
                {
                    Latitude = e.Position.Latitude,
                    Longitude = e.Position.Longitude,
                    Accuracy = e.Position.Accuracy,
                    Speed = e.Position.Speed,
                    Heading = e.Position.Heading,
                    TimeStamp = e.Position.Timestamp.DateTime
                };

                SubmitGPSLocation(e).ConfigureAwait(false);
            }
            else
            {
                CrossToastPopUp.Current.ShowToastMessage("Failed to get GPS location");
             }
        }
        catch (Exception ex)
        {
            CrossToastPopUp.Current.ShowToastMessage(ex.Message);
        }
    }

    private static async Task SubmitGPSLocation(PositionEventArgs e)
    {
        if (!NetworkCheck.IsInternet())
        {
            return;
        }

        if (!int.TryParse(App.PhoneID, out var number))
        {
            return;
        }

        try
        {
            var thetrackers = Convert.ToString(Application.Current.Properties["AuthorizedTrackers"]);

            GeneralUserPhoneLocation MyGeneralUserPhoneLocation = new GeneralUserPhoneLocation();
            MyGeneralUserPhoneLocation.PhoneID = int.Parse(App.PhoneID);
            MyGeneralUserPhoneLocation.Latitude = e.Position.Latitude.ToString("n6");
            MyGeneralUserPhoneLocation.Longitude = e.Position.Longitude.ToString("n6");

            MyGeneralUserPhoneLocation.Accuracy = e.Position.Accuracy;
            MyGeneralUserPhoneLocation.Heading = e.Position.Heading;
            MyGeneralUserPhoneLocation.Speed = e.Position.Speed;
            MyGeneralUserPhoneLocation.TimeStamp = e.Position.Timestamp.DateTime;

            MyGeneralUserPhoneLocation.RequestType = "N";
            MyGeneralUserPhoneLocation.Comment = thetrackers;

            string servicestring = JsonConvert.SerializeObject(MyGeneralUserPhoneLocation);
            HttpContent theusercontent = new StringContent(servicestring, Encoding.UTF8, "application/json");

            using (HttpClient client = new HttpClient())
            {
                client.BaseAddress = new Uri("https://mygpswebapi.com");
                var response = await client.PostAsync("Home/SaveGeneralUserPhoneLocationAPP/", theusercontent).ConfigureAwait(true);

                if (response.IsSuccessStatusCode)
                {
                   
                }
                else
                {
                }
            }
        }
        catch (Exception ex)
        {
            CrossToastPopUp.Current.ShowToastMessage(ex.Message);
        }
    }