Golang readline and writeline

readwrite.go

func readLines(path string) ([]string, error) {
  file, err := os.Open(path)
  if err != nil {
    return nil, err
  }
  defer file.Close()

  var lines []string
  scanner := bufio.NewScanner(file)
  for scanner.Scan() {
    lines = append(lines, scanner.Text())
  }
  return lines, scanner.Err()
}

// writeLines writes the lines to the given file.
func writeLines(lines []string, path string) error {
  file, err := os.Create(path)
  if err != nil {
    return err
  }
  defer file.Close()

  w := bufio.NewWriter(file)
  for _, line := range lines {
    fmt.Fprintln(w, line)
  }
  return w.Flush()
}

replace

fmt.Fprintln(w, line)

with

writer.WriteString(line)

TheFprintln adds \n or \r\n depending on OS. But the WriteString doesn't.

var nl = fmt.Sprintln() // new line, depending on OS

// [...]

w.WriteString(line)
w.WriteString(nl)

Hah. It seems Go every time uses \n. Interesting.
Thus,

w.WriteString(line)
w.WrieByte('\n')

why you don't handle err from fmt.Fprintln(w, line)?
wouldn't it be better to write like this

...
for _, line := range lines {
    _, err = fmt.Fprintln(w, line)
    if err != nil {
        return err
    }
}
...