small fix, don't worry about it

backend/internal/downloader/engine.go

@@ -0,0 +1,8 @@
+package downloader
+
+import "context"
+
+type Engine interface {
+	Add(ctx context.Context, source string) (string, error)
+	Status(ctx context.Context, id string) (string, error)
+}

backend/internal/downloader/worker.go

@@ -0,0 +1,34 @@
+package downloader
+
+import (
+	"context"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+type Worker struct {
+	log *zap.Logger
+}
+
+func NewWorker(log *zap.Logger) *Worker {
+	return &Worker{log: log}
+}
+
+func (w *Worker) Name() string {
+	return "downloader-monitor"
+}
+
+func (w *Worker) Start(ctx context.Context) error {
+	ticker := time.NewTicker(30 * time.Second)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case <-ticker.C:
+			w.log.Debug("downloader heartbeat")
+		}
+	}
+}