创建在总线上包装订阅和发布的异步方法

我有一种实现此接口的总线:

public interface IBus
{
    void Publish<T>(T t);
    void Subscribe<T>(Guid subscriptionId, Action<T> action);
    void Unsubscribe<T>(Guid subscriptionId);
}

下面是我如何使用它的示例:

public void PrintName()
{
    IBus bus = new Bus();
    var id = Guid.NewGuid();
    bus.Subscribe<ReplyUserName>(id, replyUserName =>
    {
        bus.Unsubscribe<ReplyUserName>(id);
        Console.WriteLine(replyUserName.UserName);
    });

    Bus.Publish(new RequestUserName());
}

下面是RequestUserName和ReplyUserName类:

public class RequestUserName {}

public class ReplyUserName
{
    public string UserName { get; set; }
}

然而,我想写一个扩展方法,用异步来包装它:

public static class BusExtension
{
    public static async Task<TResult> Request<TRequest, TResult>(this IBus bus, TRequest request)
    {
        // TODO...
    }
}

因此,我将能够以这样的方式编写前面的代码:

public async void PrintName()
{
    IBus bus = new Bus();
    var replyUserName = await bus.Request<RequestUserName, ReplyUserName>(new RequestUserName());
    Console.WriteLine(replyUserName.UserName);
}

我应该写什么来代替TODO?