$this->app['cache.store'] Class cache.store does not exist

This is what I'm trying to do in my service provider in Lumen

public function register()
{
    $this->app->singleton(Api::class, function() {

        return new Api($this->app['cache.store']);

    });
}

Is this a bug?

I'm using the latest version and according to this issue it should've been fixed:

• https://github.com/laravel/lumen-framework/issues/161