Constructor - Assigning class variables

Code:

class Home extends BaseController
{
    var $cache;

    public function __contruct()
    {
        parent::__construct();
        $this->cache = \Config\Services::cache();
    }
    public function reset()
    {
        $this->cache->clean();
    }
}

assume i have create a web cache.

the idea is i dont want to keep assign the same $cache in every method.

So contructor should do the job.

but when i load the page, it shows -> Undefined variable: cache

how to fix my code/this issue?