golang csv 解析

package main

import (
	"bytes"
	"encoding/csv"
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"os"
)

var (
	fileName = "test.csv"
	mode     string
)

type Book struct {
	Author string
	Title  string
}

func (book *Book) toSlice() []string {
	return []string{book.Author, book.Title}
}

func toCSV(lines [][]string, w io.Writer) error {
	n := csv.NewWriter(w)
	for _, line := range lines {
		err := n.Write(line)
		if err != nil {
			return err
		}
	}
	n.Flush()
	return n.Error()
}

func writeCSV() error {
	// init
	books := []Book{
		Book{
			Author: "F Scott Fitzgerald",
			Title:  "The Great Gatsby",
		},
		Book{
			Author: "J D Salinger",
			Title:  "The Catcher in the Rye",
		},
	}

	var items [][]string
	for _, book := range books {
		items = append(items, book.toSlice())
	}

	buffer := new(bytes.Buffer)
	if err := toCSV(items, buffer); err != nil {
		return err
	}

	// save to files
	f, err := os.Create(fileName)
	defer f.Close()
	if err != nil {
		return err
	}
	_, err = f.WriteString(buffer.String())

	return err
}

func readCSV() error {
	f, err := ioutil.ReadFile(fileName)
	if err != nil {
		return err
	}
	buffer := bytes.NewBufferString(string(f))

	csvReader := csv.NewReader(buffer)
	csvReader.Comma = ';'
	csvReader.Comment = '-'

	records, err := csvReader.ReadAll()
	if err != nil {
		return err
	}

	fmt.Println(records)
	return nil
}

func main() {
	flag.StringVar(&mode, "mode", "", "read/write csv file")
	flag.Parse()

	switch mode {
	case "write":
		writeCSV()
	case "read":
		readCSV()
	default:
		flag.Usage()
	}
}