tip ：bufio 读写存入缓存时 如果程序挂了就会丢失数据！

      
      file, err := os.Open("./test.txt") //只读方式打开  
      if err != nil {
           fmt.Println("open file failed , err ", err)
      }

      defer file.Close()

      reader := bofio.NewReader(file)
      // for 循环 读取所有内容直到 os.EOF 结束
      for {
         line , err := reader.ReadString("\n")  //读取一行内容   
         if err == os.EOF {
            break
         }
         if err != nil {
             fmt.Println("read file failed , err ", err)
            return 
         }
         fmt.Println(line)
      }