title: tornado v6 seems to have dropped tornado.web.asynchronous coroutine. any different way of fixing this in code?
body: <p>Migrated torando v5.1 to v6. but asynchronous coroutine seems to have removed. Any suggestions for its fix?</p>
  
  <p>Migrating the project from 2.7 to 3.6, at the same time moving tornado framework from v5.1 to v6.0.2 due to the bug suggested in this [<a href="https://stackoverflow.com/questions/55427108/python-code-for-dynamodb-query-is-working-on-v3-6-but-not-working-in-python-2-7]">Python code for DynamoDB query is working on v3.6 but not working in python 2.7</a> strackoverflow thread. </p>
  
  <p>After installing v6 tornado it is breaking with below error. </p>
  
  <pre><code>Python3 xxxx.py
  
  Traceback (most recent call last):
    File "XXXX.py", line 200, in &lt;module&gt;
      class MainHandler(tornado.web.RequestHandler):
    File "XXXX.py", line 201, in MainHandler
      @tornado.web.asynchronous
  AttributeError: module 'tornado.web' has no attribute 'asynchronous'
  </code></pre>
  
  <p>Come across <a href="https://github.com/mher/flower/issues/878" rel="nofollow noreferrer">https://github.com/mher/flower/issues/878</a> thread facing the same issue. is there a fix for this? or any alternative way of presenting things in code?</p>