爬虫，用协程下载图片中TypeError: a bytes-like object is required, not 'coroutine'

async def aio_download(img_url, img_name):
    async with aiohttp.ClientSession() as session:
        async with session.get(img_url) as resp:
            async with aiofiles.open('img/' + img_name, mode='ab') as f:
                await f.write(resp.read())
                print(img_name, "下载完毕！")

刚开始的下载代码是这个样子的，但是程序运行的时候一直报错TypeError，我一直以为是代码里f.write(resp.read())的输入的类型不对，到处找，最后发现是少了一个await的问题最终的代码如下：

async def aio_download(img_url, img_name):
    async with aiohttp.ClientSession() as session:
        async with session.get(img_url) as resp:
            async with aiofiles.open('img/' + img_name, mode='ab') as f:
                img = await resp.read()
                await f.write(img)
                print(img_name, "下载完毕！")