static async Task QueueAsync() { var orders = new Queue<string>(); Task order1 = Task.Run(() => PlaceOrderQueue(orders, "ushio")); Task order2 = Task.Run(() => PlaceOrderQueue(orders, "yamada")); Task order3 = Task.Run(() => PlaceOrderQueue(orders, "higuchi")); Task order4 = Task.Run(() => PlaceOrderQueue(orders, "taro")); Task.WaitAll(order1, order2, order3, order4); while(orders.Count != 0) { Co