code: func renderBuild(c *router.Context, bp *ui.BuildPage, err error) error {
  	if err != nil {
  		return err
  	}
  
  	bp.StepDisplayPref = getStepDisplayPrefCookie(c)
  
  	templates.MustRender(c.Context, c.Writer, "pages/build.html", templates.Args{
  		"BuildPage": bp,
  	})
  	return nil
  }
docs: // renderBuild is a shortcut for rendering build or returning err if it is not nil.