code: func RandText(num int) string {
  	textNum := len(txtChars)
  	text := ""
  	r := rand.New(rand.NewSource(time.Now().UnixNano()))
  
  	for i := 0; i < num; i++ {
  		text = text + string(txtChars[r.Intn(textNum)])
  	}
  	return text
  }
docs: //生成随机字体.