How to call HTTClient API call using iOS background session?

I have a requirement to create a background Task to fetch API calls, using Xamarin.iOS. The API calls are fetched using NSUrlSession CreateDownloadTask, was able to fetch the API contents without any issues. But app's legacy API code was written using HTTPClient library & when calling HTTPClient GetAsync methods and moving the app to the background is causing this error

NSURLErrorDomain - Lost connection to background transfer service.

Following is the code used to create HTTPClient background service

var configuration = NSUrlSessionConfiguration.CreateBackgroundSessionConfiguration(BackgroundSessionId);
                    configuration.HttpMaximumConnectionsPerHost = 6;
                    configuration.NetworkServiceType = NSUrlRequestNetworkServiceType.Background; 
                    configuration.AllowsCellularAccess = true;
                    configuration.WaitsForConnectivity = true;
                    configuration.AllowsConstrainedNetworkAccess = true;
                    configuration.AllowsExpensiveNetworkAccess = true;
                    configuration.ShouldUseExtendedBackgroundIdleMode = true; 
                    configuration.TimeoutIntervalForRequest = 600.0;
                    configuration.TimeoutIntervalForResource = 1200.0;
    var handler = new NSUrlSessionHandler(configuration);
                var httpClient = new HttpClient(handler);
                var response = await httpClient.GetAsync(APIURL_DOWNLOAD);
                using (var content = response.Content)
                    var result = await content.ReadAsStringAsync();

I Would like to know a workaround to achieve HTTPClient calls in the background.

Thanks in advance

How many English words
do you know?
Test your English vocabulary size, and measure
how many words do you know
Online Test
Powered by Examplum