from asyncio import *
l = Lock()

async def test():
  await l.acquire()
  print("Lock acquired")
  
async def test2():
  await l.acquire()
  loop.call_soon(trigger)
  
def trigger():
  t1.cancel()
  l.release()

loop = get_event_loop()
ensure_future(test2())
t1 = ensure_future(test())
t2 = ensure_future(test())
t3 = ensure_future(test())
loop.run_forever()