code: function validateTicket(req, options, callback) {
    var query = {
      service: utils.getPath('service', options),
      ticket: req.query.ticket
    };
    var logger = utils.getLogger(req, options);
  
    if (options.paths.proxyCallback) query.pgtUrl = utils.getPath('pgtUrl', options);
  
    var casServerValidPath = utils.getPath('serviceValidate', options) + '?' + queryString.stringify(query);
  
    logger.info('Sending request to: "' + casServerValidPath + '" to validate ticket.');
    var startTime = Date.now(); 
    utils.getRequest(casServerValidPath, function(err, response) {
      /* istanbul ignore if */
      logger.access('|GET|' + casServerValidPath + '|' + (err ? 500 : response.status) + "|" + (Date.now() - startTime));
      if (err) {
        logger.error('Error when sending request to CAS server, error: ', err.toString());
        logger.error(err);
        return callback(err);
      }
  
      callback(null, response);
    });
  }
docs: Validate ticket from CAS server
  
  @param req
  @param options
  @param callback