Add doc.

log/examples_test.go

@@ -47,7 +47,7 @@ func ExampleModule() {
 	// level=ERROR msg=error
 }
 
-func ExampleModule_withAttr() {
+func ExampleWith() {
 	loggerOption := slog.HandlerOptions{
 		AddSource:   false, // Remove code position from the output for predictable test output.
 		ReplaceAttr: removeTimeAttr,

log/log.go

@@ -1,3 +1,6 @@
+// Package log is a module injecting a `*slog.Logger` instance.
+// It provides a group of functions to log with the injected instance.
+// See [examples_test.go](./examples_test.go) for the usage.
 package log
 
 import (
@@ -9,18 +12,23 @@ import (
 )
 
 var (
+	// Module for injecting `*slog.Logger`
 	Module = module.New[*slog.Logger]()
 
+	// TextLogger provides a instance with `slog.TextHandler` logging to `os.Stderr`
 	TextLogger = Module.ProvideWithFunc(func(ctx context.Context) (*slog.Logger, error) {
 		handler := slog.NewTextHandler(os.Stderr, nil)
 		return slog.New(handler), nil
 	})
+
+	// JSONLogger provides a instance with `slog.JSONHandler` logging to `os.Stderr`
 	JSONLogger = Module.ProvideWithFunc(func(ctx context.Context) (*slog.Logger, error) {
 		handler := slog.NewJSONHandler(os.Stderr, nil)
 		return slog.New(handler), nil
 	})
 )
 
+// With creates a new `context.Context` with new attrs. It's similar to [`slog.Logger.With()`](https://pkg.go.dev/log/slog#Logger.With).
 func With(ctx context.Context, args ...any) context.Context {
 	if len(args) == 0 {
 		return ctx
@@ -36,6 +44,8 @@ func With(ctx context.Context, args ...any) context.Context {
 	return Module.With(ctx, logger)
 }
 
+// DEBUG logs with the injected instance at DEBUG level.
+// If no injected `*slog.Logger`, the function does nothing.
 func DEBUG(ctx context.Context, msg string, args ...any) {
 	logger := Module.Value(ctx)
 	if logger == nil {
@@ -45,6 +55,8 @@ func DEBUG(ctx context.Context, msg string, args ...any) {
 	logger.DebugContext(ctx, msg, args...)
 }
 
+// INFO logs with the injected instance at INFO level.
+// If no injected `*slog.Logger`, the function does nothing.
 func INFO(ctx context.Context, msg string, args ...any) {
 	logger := Module.Value(ctx)
 	if logger == nil {
@@ -54,6 +66,8 @@ func INFO(ctx context.Context, msg string, args ...any) {
 	logger.InfoContext(ctx, msg, args...)
 }
 
+// WARN logs with the injected instance at WARN level.
+// If no injected `*slog.Logger`, the function does nothing.
 func WARN(ctx context.Context, msg string, args ...any) {
 	logger := Module.Value(ctx)
 	if logger == nil {
@@ -63,6 +77,8 @@ func WARN(ctx context.Context, msg string, args ...any) {
 	logger.WarnContext(ctx, msg, args...)
 }
 
+// ERROR logs with the injected instance at ERROR level.
+// If no injected `*slog.Logger`, the function does nothing.
 func ERROR(ctx context.Context, msg string, args ...any) {
 	logger := Module.Value(ctx)
 	if logger == nil {

module.go

@@ -1,5 +1,5 @@
 // Package module provides a way to do dependency injection, with type-safe, without performance penalty.
-// See [examples](#example-Module) for the basic usage.
+// See [examples_test.go](./examples_test.go) for the basic usage.
 package module
 
 import (