public Task <string> TestCall(string arg) { return(Task.Run(async() => { Console.WriteLine($"TestCall called from {_callContext.CallerInfo.Name}: {arg}"); var str = await _callContext.GetCallbackChannel <ITestCallbackService>().TestCallbackAsync("Hello!"); Console.WriteLine($"Callback from {_callContext.CallerInfo.Name} returned: {str}"); return $"TestCall received: {arg}"; })); }