code: func (app *Application) initialize() error {
  	if app.screen == nil {
  		if app.screen, app.err = tcell.NewScreen(); app.err != nil {
  			return app.err
  		}
  		app.screen.SetStyle(app.style)
  	}
  	return nil
  }
docs: // initialize initializes the application.  It will normally attempt to
  // allocate a default screen if one is not already established.