Add structured logging and better error handling

internal/logging/logging.go

@@ -0,0 +1,33 @@
+package logging
+
+import (
+	"fmt"
+	"log/slog"
+	"os"
+	"strings"
+)
+
+func Setup(level, format string) error {
+	var parsedLevel slog.Level
+	if err := parsedLevel.UnmarshalText([]byte(level)); err != nil {
+		return fmt.Errorf("LOG_LEVEL must be debug, info, warn or error: %w", err)
+	}
+	options := &slog.HandlerOptions{Level: parsedLevel}
+
+	var handler slog.Handler
+	switch strings.ToLower(format) {
+	case "text":
+		handler = slog.NewTextHandler(os.Stdout, options)
+	case "json":
+		handler = slog.NewJSONHandler(os.Stdout, options)
+	default:
+		return fmt.Errorf("LOG_FORMAT must be text or json, got %q", format)
+	}
+	slog.SetDefault(slog.New(handler))
+	return nil
+}
+
+func Fatal(message string, err error, attributes ...any) {
+	slog.Error(message, append(attributes, "error", err)...)
+	os.Exit(1)
+}