async def application(scope, receive, send):
    assert scope['type'] == 'http'

    body = b''
    while True:
        m = await receive()
        body += m.get('body', b'')
        if not m.get('more_body', False):
            break

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            (b'content-length', str(len(body)).encode()),
        ]
    })

    await send({
        'type': 'http.response.body',
        'body': body,
    })