Get File Eleman in file

getline.go

// n = file line number
func getLine(filename string, n int) (string, error) {
	if n < 1 {
		return "", fmt.Errorf("invalid request: line %d", n)
	}
	f, err := os.Open(filename)
	if err != nil {
		return "", err
	}
	defer f.Close()
	bf := bufio.NewReader(f)
	var line string
	for lnum := 0; lnum < n; lnum++ {
		line, err = bf.ReadString('\n')
		if err == io.EOF {
			switch lnum {
			case 0:
				return "", errors.New("no lines in file")
			case 1:
				return "", errors.New("only 1 line")
			default:
				return "", fmt.Errorf("only %d lines", lnum)
			}
		}
		if err != nil {
			return "", err
		}
	}
	if line == "" {
		return "", fmt.Errorf("line %d empty", n)
	}
	return line, nil
}