Logging in Go - logrus

0-intro.md

Introduction

A basic implementation of logging with Go language. Copied from https://www.honeybadger.io/blog/golang-logging/

Usage

1. Run the following commands to test with built-in log package. Logs will be saved in logs.txt.

go run log.go

2. Run the following commands to test with built-in logr package.

go get github.com/sirupsen/logrus
go run log.go

Notes

1. Time-stamps in logs - when using either log or sirupsen/logrus - can be modified by setting the TZ environment variable in the shell.
2. Built in log package is the simplest for generating file name and number.
3. For JSON formatting of logs, use sirupsen/logrus.

log.go

package main

import (
    "log"
    "os"
)

var (
    WarningLogger *log.Logger
    InfoLogger    *log.Logger
    ErrorLogger   *log.Logger
)

func init() {
    file, err := os.OpenFile("logs.txt", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0666)
    if err != nil {
        log.Fatal(err)
    }

    InfoLogger = log.New(file, "INFO: ", log.Ldate|log.Ltime|log.Lshortfile)
    WarningLogger = log.New(file, "WARNING: ", log.Ldate|log.Ltime|log.Lshortfile)
    ErrorLogger = log.New(file, "ERROR: ", log.Ldate|log.Ltime|log.Lshortfile)
}

func main() {
    InfoLogger.Println("Starting the application...")
    InfoLogger.Println("Something noteworthy happened")
    WarningLogger.Println("There is something you should know about")
    ErrorLogger.Println("Something went wrong")
}

logr.go

package main

import (
  log "github.com/sirupsen/logrus"
)

func main() {
	log.SetReportCaller(true)
	log.SetFormatter(&log.JSONFormatter{})

	log.Debug("Useful debugging information.")
	log.Info("Something noteworthy happened!")
	log.Warn("You should probably take a look at this.")
	log.Error("Something failed but I'm not quitting.")
}