class LifespanManager:
    def __init__(self, app):
        self.app = app
        self.startup_complete = asyncio.Event()
        self.shutdown_complete = asyncio.Event()
        self.messages = [{'type': 'lifespan.startup'}, {'type': 'lifespan.shutdown'}]

    async def __aenter__(self):
        self.task = asyncio.create_task(self.app(self.receive, self.send))
        await self.startup_complete.wait()

    async def __aexit__(self, ...):
        await self.shutdown_complete.wait()
        await self.task

    async def receive(self):
        return self.messages.pop()

    async def send(self, message):
        if message['type'] == 'lifespan.startup.complete':
            self.startup_complete.set()
        elif message['type'] == 'lifespan.shutdown.complete':
            self.shutdown_complete.set()