Add async/Task support for event handlers

[JakeSmokie]

I would like to request a feature to allow asynchronous event handlers using the Task type. This would enable more flexibility and performance for handling complex or long-running events.

Currently, the GameEventHandler<T> delegate only accepts a HookResult as the return type, which limits the use of async and await keywords. For example, in this code snippet:

public delegate HookResult GameEventHandler<T>(T @event, GameEventInfo info) where T : GameEvent;

public void RegisterEventHandler<T>(GameEventHandler<T> handler, HookMode hookMode = HookMode.Post) where T : GameEvent
{
    var name = typeof(T).GetCustomAttribute<EventNameAttribute>()?.Name;
    RegisterEventHandlerInternal(name, handler, hookMode == HookMode.Post);
}

There is no way to make the handler parameter an async function that returns a Task<HookResult>.

I propose adding a new delegate type, such as AsyncGameEventHandler<T>, that supports Task<HookResult> as the return type, and a corresponding method to register it, such as RegisterAsyncEventHandler<T>. This would allow users to write event handlers like this:

public async Task<HookResult> OnPlayerDeath(PlayerDeathEvent @event, GameEventInfo info)
{
    // Do some async work here
    await Task.Delay(1000);
    // Return the hook result
    return HookResult.Continue;
}

This feature would be very useful for scenarios where the event handler needs to perform some asynchronous operations, such as database queries, web requests, or other I/O tasks. It would also improve the responsiveness and scalability of the game server by avoiding blocking the main thread.

Thank you for your consideration.

[roflmuffin]

If we do support Async game event handlers, then they would have to return void (or just Task in this case), since the game thread needs to immediately know whether or not to block the event, so hook result is somewhat useless in that context.

[JakeSmokie]

Yep, I think in those cases we don't need HookResult.
We can use Task as result type.

[roflmuffin]

We would also need to make a copy of the game event values (as a readonly version), since the actual game event values disappear as soon as the next frame occurs