code: public function onPrerenderPost(PrerenderEvent $events) 
      {
          $cache = $this->getServiceLocator()->get($this->moduleOptions->getCacheKey());
          $response = $events->getResponse();
          $key = $this->getCacheEntryKey($events->getRequest());
          $cache->setItem($key, $events->getResponse());
          
          return $this;
      }
docs: Putting in cache the response.
  We arrive here if no valid cache entry found
  
  @param EventManagerInterface $events
  @return PrerenderListener