code: func (c *Client) MapCloudIPtoServer(identifier string, serverid string) error {
  	server, err := c.Server(serverid)
  	if err != nil {
  		return err
  	}
  	if len(server.Interfaces) == 0 {
  		return fmt.Errorf("Server %s has no interfaces to map cloud ip %s to", server.Id, identifier)
  	}
  	destination := server.Interfaces[0].Id
  	err = c.MapCloudIP(identifier, destination)
  	if err != nil {
  		return err
  	}
  	return nil
  }
docs: // MapCloudIPtoServer is a convenience method to map a Cloud IP to a
  // server. First looks up the server to get the network interface id. Uses the
  // first interface found.