Make RenderController Index action async

[umbracotrd]

The RenderController.cs > Index action is synchronous which prevents the derived classes call async methods inside Index method.

There was a discussion in the forum a while ago and there were few hacky ways to do it but this era of asynchronous programming, I think it would be nice that umbraco cms supports this out of the box.

[bjarnef]

It is mentioned in docs here how to used async action.
https://docs.umbraco.com/umbraco-cms/reference/routing/custom-controllers#example-hijacking-route-requests-to-a-product-page

You would need to hide the default inherited action with [NonAction]:

public class ProductPageController : RenderController
{
    [NonAction]
    public sealed override IActionResult Index() => throw new NotImplementedException();
    public async Task<IActionResult> Index(CancellationToken cancellationToken)
    {
        await SomethingAsync(cancellationToken);
        return CurrentTemplate(CurrentPage);
    }
}

[umbracotrd]

Thanks @bjarnef , I should've rtfm 😅