async def read_body(receive):
     body = b''
     more_body = True

     while more_body:
         message = await receive()
         body += message.get('body', b'')
         more_body = message.get('more_body', False)
     return body


 async def app(scope, receive, send):
     body = await read_body(receive)
     await send({
         'type': 'http.response.start',
         'status': 200,
         'headers': [
             [b'content-type', b'text/plain'],
         ]
     })
     await send({
         'type': 'http.response.body',
         'body': body,
     })