Cakephp 3 RSS error

Question

I want to make an RSS generator, I followed the tutorial of the same in http://book.cakephp.org/3.0/en/views/helpers/rss.html. But things are not working as they should, because according to the documentation, when I access the route of the item, with the extension . rss, it should return the RSS, in my case is the controller posts

/posts/index.rss

But when I try this, it tries to find a controller, and returns me the controller error not found

The action index.rss is not defined in PostsController

Note: I declared the Router::extensions('rss'); also contains ::initialize() with loadComponent('RequestHandler');

Do you know the error? Is there any practical example?