Sans I/O?

[florimondmanca]

Please describe your problem
The main API is currently the asynchronous call to the protocol object, e.g. await proto({"type": "start"}), which means it cannot be used in environments that rely on regular functions instead of async ones (such as gevent).

Describe the solution you'd like
Sans I/O encourages implementing network protocols without making any I/O nor assumptions on the underlying concurrency model (e.g.sync vs async).

This library is arguably higher-level than the ones listed on the Sans I/O project landing page (libraries for WebSocket, HTTP/2, etc), so I'm not sure whether Sans I/O principles can apply here in theory, but… My gut feeling is that there should be a way to bake it into this library.

Additional context
A very interesting discussion about this kind of endeavour happened here: aiortc/aioquic#4
Interesting ideas included thinking in terms of events and having providing an iterator interface for polling and dealing with these events.