code: func (cli *Client) SwarmUpdate(ctx context.Context, version swarm.Version, swarm swarm.Spec, flags swarm.UpdateFlags) error {
  	query := url.Values{}
  	query.Set("version", strconv.FormatUint(version.Index, 10))
  	query.Set("rotateWorkerToken", fmt.Sprintf("%v", flags.RotateWorkerToken))
  	query.Set("rotateManagerToken", fmt.Sprintf("%v", flags.RotateManagerToken))
  	query.Set("rotateManagerUnlockKey", fmt.Sprintf("%v", flags.RotateManagerUnlockKey))
  	resp, err := cli.post(ctx, "/swarm/update", query, swarm, nil)
  	ensureReaderClosed(resp)
  	return err
  }
docs: // SwarmUpdate updates the swarm.