Zend certified PHP/Magento developer

Redirect to login with add cart button for guess user

I’m trying redirect to the login when some guess user press the add cart button and he is not registered. But i can’t do it. I am usin a Observer, with the following event


this is my /app/code/vendor/module/etc/frontend/event.xml

event.xml

< ?xml version="1.0"?>

    
        
    

and my Observer/app/code/vendor/module/Observer/ForceLogin.php

ForceLogin.php

< ?php

namespace vendormoduleObserver;

use MagentoFrameworkEventObserverInterface;

class ForceLogin implements ObserverInterface
{
    protected $_responseFactory;
    protected $_url;
    private $scopeConfig;
    private $customerSession;
    private $customerUrl;
    private $context;
    private $contextHttp;
    protected $redirect;

    public function __construct(
        MagentoFrameworkAppConfigScopeConfigInterface $scopeConfig,
        MagentoFrameworkAppActionContext $context,
        MagentoCustomerModelSession $customerSession,
        MagentoFrameworkAppHttpContext $contextHttp,
        MagentoCustomerModelUrl $customerUrl,
        MagentoFrameworkAppResponseFactory $responseFactory,
        MagentoFrameworkAppResponseRedirectInterface $redirect,
        MagentoFrameworkUrlInterface $url
    ) {
        $this->scopeConfig     = $scopeConfig;
        $this->context         = $context;
        $this->customerSession = $customerSession;
        $this->customerUrl     = $customerUrl;
        $this->contextHttp     = $contextHttp;
        $this->messageManager = $context->getMessageManager();
        $this->_responseFactory = $responseFactory;
        $this->_url = $url;
        $this->redirect = $redirect;
    }

    public function execute(MagentoFrameworkEventObserver $observer)
    {
        $isLoggedIn = $this->contextHttp->getValue(MagentoCustomerModelContext::CONTEXT_AUTH);

        if (!$isLoggedIn ) {
            $this->messageManager->addError(__('Loggin First.'));
            $customRedirectionUrl = $this->_url->getUrl('customer/account/login');
            $this->_responseFactory->create()->setRedirect($customRedirectionUrl)->sendResponse('200');
            exit();
        }
        return $this;
    }
}

Any idea why he is not doing the redirect?