This seems to be conflating several issues. Async just means non-blocking. Queue a unit of work (ie: Task) to the runtime scheduler and come back to it later.
How you implement that can be with the underlying async/await or with your own custom framework. There are many examples like Actor frameworks (Akka.net, Microsoft Orleans) or System.Channels<> or anything else.
You don't need a rewrite from zero, it's pretty easy to have a class with a while(true) loop contained in an async function processing things from a System.Channel<> and that will handle things on a single thread, while you enqueue work from anywhere. You can even use the BackgroundService base class to start from: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/ho...
How you implement that can be with the underlying async/await or with your own custom framework. There are many examples like Actor frameworks (Akka.net, Microsoft Orleans) or System.Channels<> or anything else.
You don't need a rewrite from zero, it's pretty easy to have a class with a while(true) loop contained in an async function processing things from a System.Channel<> and that will handle things on a single thread, while you enqueue work from anywhere. You can even use the BackgroundService base class to start from: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/ho...