code: func Helper(u *url.URL) (*connhelper.ConnectionHelper, error) {
  	sp, err := SpecFromURL(u)
  	if err != nil {
  		return nil, err
  	}
  	return &connhelper.ConnectionHelper{
  		ContextDialer: func(ctx context.Context, addr string) (net.Conn, error) {
  			return commandconn.New(ctx, "kubectl", "--context="+sp.Context, "--namespace="+sp.Namespace,
  				"exec", "--container="+sp.Container, "-i", sp.Pod, "--", "buildctl", "dial-stdio")
  		},
  	}, nil
  }
docs: // Helper returns helper for connecting to a Kubernetes pod.
  // Requires BuildKit v0.5.0 or later in the pod.