public function get($key, $default = null)
    {
        if ($this->has($key)) {
            return $this->storage[$key] == null
                ? $default
                : $this->storage[$key];
        }

        if ($default !== null) {
            if (is_callable($default)) {
                return call_user_func($default);
            }

            return $default;
        }

        return null;
    }