discovery/marathon/marathon.go
func targetEndpoint(task *task, port uint32, containerNet bool) string {

	var host string

	// Use the task's ipAddress field when it's in a container network
	if containerNet && len(task.IPAddresses) > 0 {
		host = task.IPAddresses[0].Address
	} else {
		host = task.Host
	}

	return net.JoinHostPort(host, fmt.Sprintf("%d", port))
}
func targetEndpoint(task *task, port uint32, containerNet bool) string {

	var host string

	// Use the task's ipAddress field when it's in a container network
	if containerNet && len(task.IPAddresses) > 0 {
		host = task.IPAddresses[0].Address
	} else {
		host = task.Host
	}

	return net.JoinHostPort(host, fmt.Sprintf("%d", port))
}
// Generate a target endpoint string in host:port format.