static void Main()
{
     Task<int> primeNumberTask = Task.Run(() =>
     {
         Thread.Sleep(3000);
         return 34;
     });

     async void DisplayPrimesCount()
     {
         int result = await primeNumberTask;
         Console.WriteLine(result); // zapis wyniku
     }

     DisplayPrimesCount();

     Console.ReadKey();
}