code: func (app *Application) PostFunc(fn func()) {
  	ev := &eventAppFunc{fn: fn}
  	ev.SetEventNow()
  	if scr := app.screen; scr != nil {
  		go func() { scr.PostEventWait(ev) }()
  	}
  }
docs: // PostFunc posts a function to be executed in the context of the
  // application's event loop.  Functions that need to update displayed
  // state, etc. can do this to avoid holding locks.