Python包- aiohttp有一个警告消息“未关闭的客户端会话”

My code is as follows:

我的代码如下:

import asyncio
import aiohttp

urls = [
    'https://www.163.com/',
    'https://www.sina.com.cn/',
    'https://www.hupu.com/',
    'https://www.csdn.net/'
]

async def get_url_data(u):
    """
    read url data
    :param u:
    :return:
    """
    print('running ', u)
    resp = await aiohttp.ClientSession().get(url=u)
    headers = resp.headers
    print(u, headers)
    return headers


async def request_url(u):
    """
    main func
    :param u:
    :return:
    """
    res = await get_url_data(u)
    return res

loop = asyncio.get_event_loop()
task_lists = asyncio.wait([request_url(u) for u in urls])
loop.run_until_complete(task_lists)
loop.close()
import async