How to set itemController in each as (ember 1.11 beta3)?

I want to try use:

{{#each content as |product index|}}
  {{index}}
{{/each}}

But my app has the itemContoller, like this:

{{#each product in content itemController='product'}}

If I set this:

{{#each content as |product index| itemController='product'}}

Could not work! I found all of the ember guides and did not find the answer.

Any help please.