public function getSession()
    {
        if ($this->_session === false) {
            $sessionId = is_callable($this->sessionKey) ? call_user_func($this->sessionKey,
                $this) : $this->headers->first($this->sessionKey);
            if ($session = session()->get($sessionId)) {
                $this->_session = $session;
            } else {
                $this->_session = null;
            }
        }

        return $this->_session;
    }