code: func (c *Client) MapCloudIP(identifier string, destination string) error {
  	_, err := c.MakeApiRequest("POST", "/1.0/cloud_ips/"+identifier+"/map",
  		map[string]string{"destination": destination}, nil)
  	if err != nil {
  		return err
  	}
  	return nil
  }
docs: // MapCloudIP issues a request to map the cloud ip to the destination. The
  // destination can be an identifier of any resource capable of receiving a Cloud
  // IP, such as a server interface, a load balancer, or a cloud sql instace.
  //
  // To map a Cloud IP to a server, first lookup the server to get it's interface
  // identifier (or use the MapCloudIPtoServer convenience method)