How to get my service every x minutes Json? (iOS/Android)

I have a service I get a JSON from a url that will define, once you get the data store them directly in the database to display them later, if I call the event synchronously works perfectly, but can not get automatically refreshed. The problem is that I want to refresh every X minutes to have "Real Time".

I tried it with the following example to see if I worked first with the console, but can not, someone

var t = Task.Run(async delegate
{
await Task.Delay(TimeSpan.FromSeconds(1.5));
return 42;
});
t.Wait();
System.Diagnostics.Debug.WriteLine(string.Format("Task t Status: {0}, Result: {1}", t.Status, t.Result));

You know how I can do? Thank´s