asgi.py

import asyncio
import contextvars

ctxvar = contextvars.ContextVar("ctx")

async def lifespan():
    ctxvar.set("spam")
    return contextvars.copy_context()

async def endpoint():
    assert ctxvar.get() == "spam"

async def main():
    ctx = await asyncio.create_task(lifespan())
    await asyncio.create_task(ctx.run(endpoint))  # doesn't work, just an example