import asyncio
import contextvars


context_var = contextvars.ContextVar("aa")


async def work(x):
    val = context_var.get("no value")
    t_id = id(asyncio.Task.current_task())
    print(f"{x} - {val} {t_id}")


async def main_async(use_new_context=False):
    print(f"Check with {'new context' if use_new_context else 'same context'}")
    context_var.set(42)
    futures = []
    context = contextvars.Context()
    for i in range(3):
        if use_new_context:
            fut = context.run(asyncio.ensure_future, work(i))
        else:
            fut = asyncio.ensure_future(work(i))
        futures.append(fut)
        context_var.set(i)
    await asyncio.wait(futures)


loop = asyncio.get_event_loop()
loop.run_until_complete(main_async(False))
loop.run_until_complete(main_async(True))

Check with same context
0 - 42 139670776814792
1 - 0 139670776814952
2 - 1 139670776815112
Check with new context
0 - no value 139670776815112
1 - no value 139670776814792
2 - no value 139670776814952