logx

README

logx

logx is a lightweight structured logging helper for Go, built on top of the standard log/slog API (Go 1.21+). It enhances the default logging capabilities with hierarchical log-level routing and automatic package/type attribution.

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Features

• Hierarchical log-level routing

logx supports overriding log levels at three levels:

1. Global log level (default for everything)
2. Package-level overrides (for example, myapp/internal/db)
3. Type-level overrides (for example, myapp/internal/db.ConnectionPool)

Priority:

type-level > package-level > global-level

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• Automatic package and type metadata

logx.For() enriches log entries with:

{
  "pkg": "myapp/module",
  "type": "Type"
}

This eliminates the need for per-module logger initialization.

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• Development vs production output

• Set Config.Pretty to enable human-readable colorized logs (via tint).
• Unset Config.Pretty for pure JSON structured logs.

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Installation

go get github.com/shvydky/logx

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Quick Start

Initialize logger

logx.Init(&logx.Config{
    Pretty:      true,
    DefaultLevel: slog.LevelInfo, // global level
    Levels: map[string]slog.Level{
        // Package-level override
        "myapp/worker": slog.LevelDebug,

        // Type-level override
        "myapp/db.ConnectionPool": slog.LevelWarn,
    },
})

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Struct-based loggers

type Worker struct{}

func (w *Worker) Run() {
    logger := logx.For(w)
    logger.Info("worker started")
}

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Example output

Development mode

INFO worker started pkg=myapp/worker type=Worker

Production (JSON)

{
  "time": "2025-01-08T12:00:34.123Z",
  "level": "INFO",
  "msg": "worker started",
  "pkg": "myapp/worker",
  "type": "Worker"
}

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How it works

logx wraps the default slog.Handler and applies hierarchical routing:

if type-level rule exists:
    use it
else if package-level rule exists:
    use it
else:
    use global level

Fast-path evaluation ensures minimal overhead.

For uses the current slog.Default() handler when the logger is created. If the default logger is replaced with slog.SetDefault, subsequent calls to For use the replacement handler; loggers returned by earlier calls keep the handler they were created with.

When using WithHandler, configure the custom handler to accept the lowest level present in Config.DefaultLevel and Config.Levels. Handler-level filtering is applied in addition to logx routing, so a custom handler can still discard a record allowed by a package- or type-level override.

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Requirements

• Go 1.21+
• github.com/lmittmann/tint

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License

MIT License

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Contributing

Issues and pull requests are welcome.

Documentation

Index

• func For(target any) *slog.Logger
• func Init(cfg *Config, opts ...Options) *slog.Logger
• type Config
• type Options
  • func WithHandler(h slog.Handler) Options
  • func WithWriter(w io.Writer) Options

Functions

func For

func For(target any) *slog.Logger

func Init

func Init(cfg *Config, opts ...Options) *slog.Logger

Types

type Config

type Config struct {

	// DefaultLevel is the default log level.
	// It is used for packages and types not listed in Levels.
	DefaultLevel slog.Level
	// Levels is a map of package or type names to log levels.
	// Package names are in the form "github.com/user/project/pkg".
	// Type names are in the form "github.com/user/project/pkg.Type".
	// Type-specific levels take precedence over package-specific levels.
	Levels map[string]slog.Level
	// Pretty enables pretty printing of log entries
	Pretty bool
	// contains filtered or unexported fields
}

Config holds the configuration for the logx logger.

type Options

type Options func(*Config)

func WithHandler

func WithHandler(h slog.Handler) Options

func WithWriter

func WithWriter(w io.Writer) Options