code: func (p *Project) Port(ctx context.Context, index int, protocol, serviceName, privatePort string) (string, error) {
  	service, err := p.CreateService(serviceName)
  	if err != nil {
  		return "", err
  	}
  
  	containers, err := service.Containers(ctx)
  	if err != nil {
  		return "", err
  	}
  
  	if index < 1 || index > len(containers) {
  		return "", fmt.Errorf("Invalid index %d", index)
  	}
  
  	return containers[index-1].Port(ctx, fmt.Sprintf("%s/%s", privatePort, protocol))
  }
docs: // Port returns the public port for a port binding of the specified service.