code: function session(options) {
      options = options || {};
      DEBUG && debug('configure http session middleware', options);
      if (options.store) {
          try {
              var storeModule = options.store.module;
              var SessionStore = require(storeModule)(express);
              // replace store options with store object
              options.store = new SessionStore(options.store.options);
              return expressSession(options);
          } catch (e) {
              console.error('failed to configure http session store', e);
              //process.exit(1);
          }
      }
      console.warn('**fallback** use default session middleware');
      return expressSession(options);
  }
docs: session middleware.
  
  @param {*} [options]
  @param {*} [options.store]
  @param {String} [options.store.module]
  @param {*} [options.store.options] store specific options
  @returns {function} connect/express middleware function
  @see https://github.com/expressjs/session