code: func loadKeyringFile(c *serf.Config) error {
  	if c.KeyringFile == "" {
  		return nil
  	}
  
  	if _, err := os.Stat(c.KeyringFile); err != nil {
  		return err
  	}
  
  	keyringData, err := ioutil.ReadFile(c.KeyringFile)
  	if err != nil {
  		return err
  	}
  
  	keys := make([]string, 0)
  	if err := json.Unmarshal(keyringData, &keys); err != nil {
  		return err
  	}
  
  	return loadKeyring(c, keys)
  }
docs: // loadKeyringFile will load a gossip encryption keyring out of a file. The file
  // must be in JSON format and contain a list of encryption key strings.