code: func GetConnectionHelper(daemonURL string) (*ConnectionHelper, error) {
  	u, err := url.Parse(daemonURL)
  	if err != nil {
  		return nil, err
  	}
  	switch scheme := u.Scheme; scheme {
  	case "ssh":
  		sp, err := ssh.ParseURL(daemonURL)
  		if err != nil {
  			return nil, errors.Wrap(err, "ssh host connection is not valid")
  		}
  		return &ConnectionHelper{
  			Dialer: func(ctx context.Context, network, addr string) (net.Conn, error) {
  				return commandconn.New(ctx, "ssh", append(sp.Args(), []string{"--", "docker", "system", "dial-stdio"}...)...)
  			},
  			Host: "http://docker",
  		}, nil
  	}
  	// Future version may support plugins via ~/.docker/config.json. e.g. "dind"
  	// See docker/cli#889 for the previous discussion.
  	return nil, err
  }
docs: // GetConnectionHelper returns Docker-specific connection helper for the given URL.
  // GetConnectionHelper returns nil without error when no helper is registered for the scheme.
  //
  // ssh://<user>@<host> URL requires Docker 18.09 or later on the remote host.