Add common logger helper

logger/logger.go

@@ -0,0 +1,82 @@
+package logger
+
+import (
+	"context"
+	"log"
+	"os"
+	"strconv"
+	"sync"
+
+	"golang.org/x/exp/slog"
+)
+
+var ConfigPrefix = ""
+
+var rootLogger *slog.Logger
+var setup sync.Once
+
+func Setup() *slog.Logger {
+
+	setup.Do(func() {
+
+		var programLevel = new(slog.LevelVar) // Info by default
+
+		envVar := "DEBUG"
+		if len(ConfigPrefix) > 0 {
+			envVar = ConfigPrefix + "_" + envVar
+		}
+
+		if opt := os.Getenv(envVar); len(opt) > 0 {
+			if debug, _ := strconv.ParseBool(opt); debug {
+				programLevel.Set(slog.LevelDebug)
+			}
+		}
+
+		logOptions := &slog.HandlerOptions{Level: programLevel}
+
+		if len(os.Getenv("INVOCATION_ID")) > 0 {
+			// don't add timestamps when running under systemd
+			log.Default().SetFlags(0)
+
+			logReplace := func(groups []string, a slog.Attr) slog.Attr {
+				// Remove time
+				if a.Key == slog.TimeKey && len(groups) == 0 {
+					a.Key = ""
+					a.Value = slog.AnyValue(nil)
+				}
+				return a
+			}
+
+			logOptions.ReplaceAttr = logReplace
+		}
+
+		logHandler := slog.NewTextHandler(os.Stderr, logOptions)
+
+		// https://github.com/cyrusaf/ctxlog/pull/1
+		// log := slog.New(ctxlog.NewHandler(logHandler))
+		log := slog.New(logHandler)
+
+		slog.SetDefault(log)
+
+		rootLogger = log
+
+	})
+
+	return rootLogger
+}
+
+type loggerKey struct{}
+
+// NewContext adds the logger to the context.
+func NewContext(ctx context.Context, l *slog.Logger) context.Context {
+	return context.WithValue(ctx, loggerKey{}, l)
+}
+
+// FromContext retrieves a logger from the context. If there is none,
+// it returns the default logger.
+func FromContext(ctx context.Context) *slog.Logger {
+	if l, ok := ctx.Value(loggerKey{}).(*slog.Logger); ok {
+		return l
+	}
+	return Setup()
+}