public function getExpiration()
    {
        if ($this->isHit() && null === $this->expiration) {
            $key = [$this->getCacheItemPool()->getPoolName(), $this->getKey()];
            $key = $this->getCacheItemPool()->getDriver()->buildKey($key);

            $this->expiration = $this->getCacheItemPool()->getDriver()->getExpiration($key);
        }

        return $this->expiration;
    }