code: func (c *Client) DecommissionVolume(appID string, vol *ct.Volume) error {
  	if appID == "" {
  		return errors.New("controller: missing app ID")
  	}
  	if vol.ID == "" {
  		return errors.New("controller: missing id")
  	}
  	return c.Put(fmt.Sprintf("/apps/%s/volumes/%s/decommission", appID, vol.ID), &vol, &vol)
  }
docs: // DecommissionVolume decommissions a volume