code: func (node *Node) StartPos() int {
  	pFirstNode, _ := strconv.Atoi(fmt.Sprintf("%d", node.head.surface))
  	pCurrentNode, _ := strconv.Atoi(fmt.Sprintf("%d", node.current.surface))
  	return utf8.RuneCountInString(C.GoStringN(node.head.surface, C.int(pCurrentNode-pFirstNode)))
  }
docs: // start pos in the text.