code: func (a *Agent) updateToken(target, token string, q *WriteOptions) (*WriteMeta, error) {
  	meta, _, err := a.updateTokenOnce(target, token, q)
  	return meta, err
  }
docs: // updateToken can be used to update one of an agent's ACL tokens after the agent has
  // started. The tokens are may not be persisted, so will need to be updated again if
  // the agent is restarted unless the agent is configured to persist them.