How to get the base URL of a site in Queue API?

I am trying to get the base url of the drupal 8 website in a queue process but I am getting http://default as the base url. What am I missing here?

  public function testUrl() {
    global $base_url;
    var_dump($base_url);
    $host = \Drupal::request()->getSchemeAndHttpHost();
    var_dump($host); // output - http://default
    $host2 = \Drupal::request()->getHost();
    var_dump($host2); // output - default
    $uri = \Drupal::request()->getUri();
    var_dump($uri); // output - http://default
    $url = \Drupal\Core\Url::fromUserInput('/', ['absolute' => TRUE])->toString();
    var_dump($url); // output - http://default
    $url_options = [
      'absolute' => TRUE,
      'language' => \Drupal::languageManager()->getCurrentLanguage(),
    ];
    $site_url = \Drupal\Core\Url::fromRoute('<front>', [], $url_options)->toString();
    var_dump($site_url); // output - http://default
    var_dump($_SERVER['SERVER_NAME']); // output - NULL
    die;
  }

The process running the queue worker will be setting that default host. For example, drush cron

You may need to set the public host name with the drush request, via uri or use a drush alias.

drush --uri=http://example.com cron

More info https://docs.drush.org/en/8.x/usage/