for-nmichaud.py

@asynccontextmanager
async def subscribe(host, port, subscription_info):
    # Make connection, with a 'with' block so we make sure to close it eventually
    async with await trio.open_tcp_stream(host, port) as stream:
        # Subscribe to whatever channel
        await msg_send(stream, subscription_info)
        # Start heartbeat task
        async with trio.open_nursery() as nursery:
            nursery.start_soon(heartbeat_sender, stream)
            # Done setting up this context manager. Return the message iterator object.
            yield receiver(stream)
            # Okay, time to tear everything down. Cancel the heartbeat_sender
            nursery.cancel_scope.cancel()
            # And when we exit the 'with' blocks here it'll close everything else
            
# Usage:
async with subscribe(host, port, subscription_info) as messages:
    async for message in messages:
        ...