slogpretty ✨

A customizable and colorful handler for Go's slog designed for structured, readable, and beautiful terminal output.

Features

• 🌈 Colored log levels (DEBUG, INFO, WARN, ERROR)
• 📝 Structured attributes with clean formatting
• 📂 Smart source tracking (file:line)
• 🪄 Multiline mode for complex data
• ⏱️ Custom timestamp formatting

Installation

go get github.com/Marlliton/slogpretty

Basic Usage

Set up slogpretty as the default handler:

package main

import (
	"log/slog"
	"os"

	"github.com/Marlliton/slogpretty"
)

func main() {
	// Minimal setup
	handler := slogpretty.New(os.Stdout, nil)
	slog.SetDefault(slog.New(handler))

	slog.Info("Server started", "port", 8080)
}

Advanced Configuration

You can configure the handler using the Options struct:

handler := slogpretty.New(os.Stdout, &slogpretty.Options{
	Level:      slog.LevelDebug,
	AddSource:  true,                            // Show file location
	Colorful:   true,                            // Enable colors. Default is true
	Multiline:  true,                            // Pretty print for complex data
	TimeFormat: slogpretty.DefaultTimeFormat,    // Custom format (e.g., time.Kitchen)
})

Features

1. Colored Levels

   Each log level has a distinct color.

2. Structured Attributes

   Clean formatting for attributes.

	slog.Debug("Debugging data")
	slog.Info("Informational message")
	slog.Warn("Potential issue detected")
	slog.Error("Operation failed")
	slog.Info("User logged in", "user_id", 1234, "email", "[email protected]", "active", true)

3. Complex Data in Multiple Lines

	slog.Info("Event with group and subgroups",
		"user", "bob",
		slog.Group("details",
			slog.Int("port", 8080),
			slog.String("status", "inactive"),
			slog.Group("metrics",
				slog.Float64("cpu", 72.5),
				slog.Float64("memory", 65.3),
			),
			slog.Group("location",
				slog.String("country", "Brazil"),
				slog.String("region", "SP"),
				slog.Group("coordinates",
					slog.Float64("lat", -23.5505),
					slog.Float64("lon", -46.6333),
				),
			),
		),
		"session", "0x93AF21",
		"authenticated", false,
	)

💡 Best Practices

🛠 Development: Enable as Many Features as You Like

In development environments, it's recommended to enable as many features as possible to improve log readability, debugging, and traceability:

&pretty.Options{
    Level:     slog.LevelDebug,
    AddSource: true,
    Colorful:  true,
    Multiline: true,
}

These options provide:

• Logs from the debug level (LevelDebug)
• Source tracking (AddSource)
• Colored output for better terminal visibility (Colorful)
• Structured multiline formatting (Multiline)

---

🚀 Production: Use slog's Native JSONHandler

For production, it's best to use slog.NewJSONHandler, which generates logs in JSON format:

JSONhandler := slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
	Level: slog.LevelInfo,
})
slog.SetDefault(slog.New(JSONhandler))

slog.Info("Event with groups and subgroups",
	"user", "bob",
	slog.Group("details",
		slog.Int("port", 8080),
		slog.String("status", "inactive"),
		slog.Group("metrics",
			slog.Float64("cpu", 72.5),
			slog.Float64("memory", 65.3),
		),
		slog.Group("location",
			slog.String("country", "Brazil"),
			slog.String("region", "SP"),
			slog.Group("coordinates",
				slog.Float64("lat", -23.5505),
				slog.Float64("lon", -46.6333),
			),
		),
	),
	"session", "0x93AF21",
	"authenticated", false,
)

✅ Why Use JSON in Production?

• Compatible with observability tools (e.g., Datadog, Loki, Grafana)
• Widely accepted format — simplifies analysis, searching, etc.
• Standardized structure — ideal for distributed systems and centralized logging
• Efficient — avoids overhead from unnecessary visual formatting