code: func (d *DropDown) SetCurrentOption(index int) *DropDown {
  	if index >= 0 && index < len(d.options) {
  		d.currentOption = index
  		d.list.SetCurrentItem(index)
  		if d.selected != nil {
  			d.selected(d.options[index].Text, index)
  		}
  		if d.options[index].Selected != nil {
  			d.options[index].Selected()
  		}
  	} else {
  		d.currentOption = -1
  		d.list.SetCurrentItem(0) // Set to 0 because -1 means "last item".
  		if d.selected != nil {
  			d.selected("", -1)
  		}
  	}
  	return d
  }
docs: // SetCurrentOption sets the index of the currently selected option. This may
  // be a negative value to indicate that no option is currently selected. Calling
  // this function will also trigger the "selected" callback (if there is one).