TYPO3 9 frontend use session with eID

use TYPO3\CMS\Frontend\Utility\EidUtility;

  public function getDateAction(ServerRequestInterface $request): ResponseInterface
	{
		$this->request = $request;

		try {
			$response = new Response();
			$queryParams = $this->request->getQueryParams();

			if($queryParams['eID'] == 'ibox') {
				$action = $queryParams['tx_ibox_eID']['action'];
				if( $action == 'set') {
					$myarr = [
						'title' => 'the name',
						'desc' => 'the description of change'
					];
					$key = 'ibox';
					echo json_encode($this->writeSession($key, $myarr));
					die();
				}

				if( $action == 'del') {
					$key = 'ibox';
					$this->unsetSession($key);
					echo 'is removed';
					die();
				}
			}
			die();

		} catch (\InvalidArgumentException $e) {
			  return (new Response)->withStatus(410);
    } catch (Exception $e) {
        return (new Response)->withStatus(404);
    }
	}

  /**
	 *
	 * @param string $key
	 * @param array $myarr
	 */
    protected function writeSession($key = '',array $myarr = [])
	{

		$this->feUserObj = EidUtility::initFeUser();

		$sessionData = serialize($myarr);
		$this->feUserObj->setKey('ses', $key, $sessionData);
		$this->feUserObj->storeSessionData();

		return $this->feUserObj->getKey('ses', $key);
    }

	/**
	 *
	 * @param string $key
	 */
	protected function unsetSession($key = '')
	{
		$this->feUserObj = EidUtility::initFeUser();
		$this->feUserObj->setKey('ses', $key, NULL);
		$this->feUserObj->storeSessionData();
	}