private static void ConcurrentDictionaryDemo()
{
var controller = new StockController();
TimeSpan workDay = new TimeSpan(0, 0, 1);
Task t1 = Task.Run(() => new SalesManager("Cody").StartWork(controller, workDay));
Task t2 = Task.Run(() => new SalesManager("Connor").StartWork(controller, workDay));
Task t3 = Task.Run(() => new SalesManager("Sean").StartWork(controller, workDay));
Task.WaitAll(t1, t2, t3);
controller.DisplayStatus();
}