slog - Lightweight, configurable, extensible Go logging library

slog is a lightweight, configurable, extensible Go logging library.

Features

• Simple, directly available without configuration
• Support common log level processing.
  • eg: trace debug info notice warn error fatal panic
• Support any extension of Handler Formatter as needed
• Supports adding multiple Handler log processing at the same time, outputting logs to different places
• Support to custom log message Formatter
  • Built-in json text two log record formatting Formatter
• Support to custom build log messages Handler
  • The built-in handler.Config handler.Builder can easily and quickly build the desired log handler
• Has built-in common log write handler program
  • console output logs to the console, supports color output
  • writer output logs to the specified io.Writer
  • file output log to the specified file, optionally enable buffer to buffer writes
  • simple output log to the specified file, write directly to the file without buffering
  • rotate_file outputs logs to the specified file, and supports splitting files by time and size, and buffer buffered writing is enabled by default
  • See ./handler folder for more built-in implementations

Output logs to file

• Support enabling buffer for log writing
• Support splitting log files by time and size
• Support configuration to compress log files via gzip
• Support clean old log files by BackupNum BackupTime

Git repository

• Github: https://github.com/gookit/slog

Install

go get github.com/gookit/slog

Quick start

package main

import (
    "github.com/gookit/slog"
)

func main() {
    slog.Trace("this is a log message")
    slog.Debug("this is a log message")
    slog.Info("this is a log message")
    slog.Notice("this is a log message")
    slog.Warn("this is a log message")
    slog.Error("this is a log message")
    slog.Fatal("this is a log message")
}

output preview:

Logs to file

Using slog to output logs to files is very convenient, and supports multiple files, splitting by time, etc.

package main

import (
    "github.com/gookit/slog"
    "github.com/gookit/slog/handler"
    "github.com/gookit/slog/rotatefile"
)

func main() {
    defer slog.MustFlush()

    // DangerLevels contains: slog.PanicLevel, slog.ErrorLevel, slog.WarnLevel
    h1 := handler.MustRotateFile("/tmp/logs/app_error.log", rotatefile.EveryHour, 
        handler.WithLogLevels(slog.DangerLevels),
    )

    // NormalLevels contains: slog.InfoLevel, slog.NoticeLevel, slog.DebugLevel, slog.TraceLevel
    h2 := handler.MustRotateFile("/tmp/logs/app_info.log", rotatefile.EveryHour,
        handler.WithLogLevels(slog.NormalLevels),
    )

    slog.PushHandler(h1)
    slog.PushHandler(h2)

    // add logs
    slog.Info("info message text")
    slog.Error("error message text")
}

See logs dir:

$ ls /tmp/logs
app_error.log
app_info.log

More usage

More usage please see README

Comments

[Samuel Berthe]

Go 1.21 is going to bring a new structured logging library called "slog".

I will be pretty similar to gookit/slog but without formatter and provided handlers will only be able to write to stdout or stdin.

The library has been built to be extended very easily with customer slog.Handler.