logging code sample by golang

logging.go

package main

import (
	"encoding/csv"
	"fmt"
	"io"
	"log"
	"os"
	"time"

	"golang.org/x/text/encoding/japanese"
	"golang.org/x/text/transform"
)

var (
	csvWriter *csv.Writer
)

func main() {
	os.Exit(run())
}

func run() int {
	// Normal logging + file
	logName := time.Now().Format("./logs/log_20060102-030405.txt")
	logfile, err := os.Create(logName)
	if err != nil {
		log.Println("Failed to create a log file.", err)
		return 1
	}
	defer logfile.Close()
	log.SetOutput(io.MultiWriter(os.Stdout, logfile))
	someFunc()

	// csv logging
	csvName := time.Now().Format("./logs/sensor_20060102-030405.csv")
	csvfile, err := os.Create(csvName)
	if err != nil {
		log.Println("Failed to create a csv file.", err)
		return 1
	}
	defer csvfile.Close()
	csvWriter = csv.NewWriter(transform.NewWriter(csvfile, japanese.ShiftJIS.NewEncoder()))
	anyFunc()
	csvWriter.Flush()

	return 0
}

func someFunc() {
	log.Println("logging!")
}

func anyFunc() {
	csvWriter.Write([]string{"Time", "Raw-Value"})
	value := 543
	csvWriter.Write([]string{
		time.Now().Format("2006/01/02 03:04:05"),
		fmt.Sprintf("%v", value),
	})
}