protected function execute(InputInterface $input, OutputInterface $output)
 {
     $cacheDir = $input->getArgument('cache');
     $text = "";
     if (file_exists($cacheDir)) {
         $gc = new GarbageCollector($cacheDir);
         if (file_exists($gc->getLockPath())) {
             unlink($gc->getLockPath());
         }
         $text .= "<info>Garbage collection unlocked.</info>" . PHP_EOL;
     } else {
         $text .= "<error>Cache directory does not exist.</error>" . PHP_EOL;
     }
     $output->writeln($text);
 }