The key to getting static files resumable during download is to implement Accept-Ranges, Content-Range and related support.

So the client/browser can request partial files with Range, e.g. Range: bytes=500-999.

This is also what makes video files seekable by standard players in browsers (improving user experience).

A helper, response.sendfile() comes for this purpose. Also with a multipart ranges support.

Usage:

# http://localhost:8000/download/myvideo.mp4

@app.route('/download/myvideo.mp4')
async def download(**server):
    # video file location
    path = '/home/Videos/myvideo.mp4'

    await server['response'].sendfile(path, content_type='video/mp4')

    # optional, to enable keep-alive
    return True

Note that this built-in feature just works. It does not use a shiny module like aiofiles for the sake of simplicity.