code: func initCookieEngine() SessionEngine {
  	ce := &SessionCookieEngine{}
  
  	var err error
  	if expiresString, ok := Config.String("session.expires"); !ok {
  		ce.ExpireAfterDuration = 30 * 24 * time.Hour
  	} else if expiresString == session.SessionValueName {
  		ce.ExpireAfterDuration = 0
  	} else if ce.ExpireAfterDuration, err = time.ParseDuration(expiresString); err != nil {
  		panic(fmt.Errorf("session.expires invalid: %s", err))
  	}
  
  	return ce
  }
docs: // Called when the the application starts, retrieves data from the app config so cannot be run until then