python3.9中 asyncio.Task.all_tasks()调用变为了asyncio.all_tasks()，但是有一个问题，在捕获KeyboardInterrupt后all_tasks = asyncio.all_tasks()无法找到当前事件循环，报错no running event loop，需要在all_tasks = asyncio.all_tasks(loop)中直接传入loop，传入参数loop后代码正常运行。查阅官方文档与谷歌搜索后无法理解为何all_tasks(None)无法找到当前event loop，遂请教老师！

# -*- coding: utf-8 -*-
import asyncio
import time
async def get(time):
	print('waiting')
	await asyncio.sleep(time)
	print(f'down after {time}s')

if __name__ == '__main__':
	starttime = time.time()
	task1 = get(2)
	task2 = get(3)
	task3 = get(3)
	tasks = [task1,task2,task3]
	loop = asyncio.get_event_loop()
	try:
		loop.run_until_complete(asyncio.wait(tasks))
	except KeyboardInterrupt as e:
		alltasks = asyncio.all_tasks(loop)
		for task in alltasks:
			print('cancel')
			print(task.cancel())
		loop.stop()
		loop.run_forever()
	finally:
		loop.close()



	print(time.time()-starttime)