为什么这个任务没有完成?

为什么按下ctrl+c时控制台应用程序不退出?

程序输出:

Press Ctrl+C to stop...
doing stuff.
doing stuff.
...
*Ctrl+C pressed*
exiting...
*never actually exits*

class Program {
    static void Main(string[] args) {
        MainAsync(args).GetAwaiter().GetResult();
    }

    private static async Task MainAsync(string[] args) {

        MyAsyncClass myAsync = new MyAsyncClass();

        var tcs = new TaskCompletionSource<object>();
        Console.CancelKeyPress += (sender, e) => { tcs.SetResult(null); };

        var task = Task.Run(() => myAsync.Start());

        await Console.Out.WriteLineAsync("Press Ctrl+C to stop...");

        await tcs.Task;
        await Console.Out.WriteLineAsync("exiting...");
    }
}

public class MyAsyncClass {
    public async Task Start() {
        while(true) {
            await Console.Out.WriteLineAsync("doing stuff.");
            Thread.Sleep(1000);
        }
    }
}