🌈 slogcolor

slogcolor is a little, customizable color handler for log/slog. It enhances log readability by color-coding log levels and supports flexible formatting options. Its output is inspired by XMRig and zerolog.

Installation

Run:

go get -u github.com/MatusOllah/slogcolor

Basic Usage

package main

import (
    "os"
    "time"
    "errors"
    "log/slog"

    "github.com/MatusOllah/slogcolor"
)

func main() {
    // Configure slog to use slogcolor by default for colored output
    slog.SetDefault(slog.New(slogcolor.NewHandler(os.Stderr, slogcolor.DefaultOptions)))

    slog.Info("Initializing")
    slog.Debug("Init done", "duration", 500*time.Millisecond)
    slog.Warn("Slow request!", "method", "GET", "path", "/api/users", "duration", 750*time.Millisecond)
    slog.Error("DB connection lost!", "err", errors.New("connection reset"), "db", "horalky")
}

Default options

slogcolor provides a set of predefined options to simplify configuration. You can use these default options via DefaultOptions, or simply pass nil for the same effect.

slog.SetDefault(slog.New(slogcolor.NewHandler(os.Stderr, slogcolor.DefaultOptions)))

// or

slog.SetDefault(slog.New(slogcolor.NewHandler(os.Stderr, nil)))

The behavior is identical in both cases, so you can choose based on your coding style or preference.

Customized output format

The output format can also be customized using the Options like this:

opts := &slogcolor.Options{
    Level:         slog.LevelDebug,
    TimeFormat:    time.RFC3339,
    SrcFileMode:   slog.Nop,
}
slog.SetDefault(slog.New(slogcolor.NewHandler(os.Stderr, opts)))

or like this:

opts := slogcolor.DefaultOptions
opts.Level = slog.LevelDebug
opts.TimeFormat = time.RFC3339
opts.SrcFileMode = slog.Nop

slog.SetDefault(slog.New(slogcolor.NewHandler(os.Stderr, opts)))

Prefixes

Prefixes can be useful for adding context to log messages, such as identifying different subsystems or components (e.g., DB, SceneController, Network) that generated the log.

Messages can be prefixed with Prefix like this:

slog.Info(slogcolor.Prefix("MyPrefix", "kajšmentke"))
slog.Info(slogcolor.Prefix("SceneController", "switching scene"), "scene", "MainMenuScene")

// or

slog.Info(slogcolor.Prefix("MyPrefix")+"kajšmentke")
slog.Info(slogcolor.Prefix("SceneController")+"switching scene", "scene", "MainMenuScene")

It can also be used as an alias for ease of use, especially when you frequently use prefixes, like this:

var P = slogcolor.Prefix

slog.Info(P("MyPrefix", "kajšmentke"))

// or

slog.Info(P("MyPrefix")+"kajšmentke")

Disable colors

Colors are enabled by default but can be disabled using Options.NoColor. Particularly useful for automatically enabling colors based on the terminal capabilities using e.g. the go-isatty package.

w := os.Stderr

opts := slogcolor.DefaultOptions
opts.NoColor = !isatty.IsTerminal(w.Fd())

slog.SetDefault(slog.New(slogcolor.NewHandler(w, opts)))

License

Licensed under the MIT License (see LICENSE)