code: func (lr *logRegistry) AddHook(hook logrus.Hook) {
  	defaultLogger.Infof("adding hook %q to registry", hook)
  	lr.hooks = append(lr.hooks, hook)
  
  	lgs := lr.ListLoggers()
  	for lg := range lgs {
  		logger, found := lr.Lookup(lg)
  		if found {
  			logger.AddHook(hook)
  		}
  	}
  }
docs: // HookConfigs stores hook configs provided by log manager
  // and applies hook to existing loggers