title: Flask how to set cross domain cookie
body: <p>I try to set a cross domain cookie with response like this:</p>
  
  <pre><code>@auth.route('/test', methods=['GET', 'POST'])
  def test():
      resp = make_response('setcookie')
      resp.set_cookie('cookie_1', 'cookie for A', domain='.A.com')
      return resp
  </code></pre>
  
  <p>but it dose not work.I can not see the cookie on '.A.com' in the browser.
  What is wrong?</p>