feat: enhance structured logging with service context and dynamic levels

Author: pirosiki197

cmd/main.go

@@ -32,10 +32,13 @@ var (
 )
 
 var rootCommand = &cobra.Command{
-	Use:              "ns",
-	Short:            "NeoShowcase",
-	Version:          fmt.Sprintf("%s (%s)", version, revision),
-	PersistentPreRun: cli.PrintVersion,
+	Use:     "ns",
+	Short:   "NeoShowcase",
+	Version: fmt.Sprintf("%s (%s)", version, revision),
+	PersistentPreRun: func(cmd *cobra.Command, args []string) {
+		serviceName := cmd.Name()
+		slogutil.InitLogger(serviceName, version, revision)
+	},
 }
 
 type component interface {
@@ -78,9 +81,6 @@ func componentCommand(name string, gen componentGenF, longDesc string) *cobra.Co
 }
 
 func main() {
-	// Initialize logger early with default level
-	slogutil.InitLogger(slog.LevelInfo)
-
 	// Initialize OpenTelemetry tracer provider for trace ID generation
 	if err := observability.InitTracerProvider("neoshowcase"); err != nil {
 		slog.Error("failed to initialize tracer provider", "error", err)

pkg/util/cli/flag.go

@@ -18,7 +18,7 @@ func SetupDebugFlag(flags *pflag.FlagSet) {
 	viper.SetDefault("debug", false)
 	cobra.OnInitialize(func() {
 		if Debug {
-			slogutil.InitLogger(slog.LevelDebug)
+			slogutil.SetLogLevel(slog.LevelDebug)
 			boil.DebugMode = true
 		}
 	})
@@ -44,6 +44,6 @@ func SetupLogLevelFlag(flags *pflag.FlagSet) {
 			slog.Error("invalid log level", "level", levelStr)
 			level = slog.LevelInfo
 		}
-		slogutil.InitLogger(level)
+		slogutil.SetLogLevel(level)
 	})
 }

pkg/util/cli/version.go

@@ -1,11 +1,5 @@
 package cli
 
-import (
-	"log/slog"
-
-	"github.com/spf13/cobra"
-)
-
 var (
 	version  string
 	revision string
@@ -19,9 +13,3 @@ func SetVersion(ver, rev string) {
 func GetVersion() (ver, rev string) {
 	return version, revision
 }
-
-// PrintVersion バージョンを出力する
-func PrintVersion(cmd *cobra.Command, _ []string) {
-	cmd = cmd.Root()
-	slog.Info("neoshowcase", "name", cmd.Use, "version", cmd.Version)
-}

pkg/util/slogutil/init.go

@@ -0,0 +1,29 @@
+package slogutil
+
+import (
+	"log/slog"
+	"os"
+)
+
+var levelVar = new(slog.LevelVar) // default level is INFO
+
+// InitLogger initializes the global slog logger with CustomHandler
+func InitLogger(service, version, revision string) {
+	opts := &slog.HandlerOptions{
+		AddSource: true,
+		Level:     levelVar,
+	}
+	handler := NewCustomHandler(os.Stdout, opts)
+	logger := slog.New(handler).With(
+		slog.Group("service",
+			"name", service,
+			"version", version,
+			"revision", revision,
+		),
+	)
+	slog.SetDefault(logger)
+}
+
+func SetLogLevel(level slog.Level) {
+	levelVar.Set(level)
+}