import asyncio

async def v(n):
    for i in range(2):
        print(n, "Waiting for lock")
        async with lock:
            print(n, "Got lock")
            await f

async def test():
    f0 = asyncio.ensure_future(v(0))
    f1 = asyncio.ensure_future(v(1))
    await asyncio.sleep(0)
    f.set_result(True)
    f1.cancel()
    await f0

lock = asyncio.Lock()
f = asyncio.Future()
loop = asyncio.get_event_loop()
loop.run_until_complete(test())