Thread-safe programming techniques

Look at this piece of code. Run it and see what happens:

using ExtensionLibrary;
int iterationCount = 100;
ThreadPool.QueueUserWorkItem(async (state) =>
{
    await Task.Delay(500);
    iterationCount = 0;
    $"We are stopping it...".Dump(ConsoleColor.Red);
});
await WaitAWhile();
$"In the main part of the app.".Dump(ConsoleColor.White);
"Main app is done.\nPress any key to stop.".Dump(ConsoleColor.White);
Console.ReadKey();
return 0;
async Task WaitAWhile()
{
    do
    {
        $"In the loop at iterations {iterationCount}".            Dump(ConsoleColor.Yellow);
        await Task.Delay(1);
    }while (--iterationCount > 0) ;
}

We have a Task...