as function instead

builder.go

@@ -9,15 +9,26 @@ type FunctionalComponent struct {
 }
 
 func NewFunctionalComponent(
-	init func(ctx context.Context) error,
-	start func(ctx context.Context) error,
-	stop func(ctx context.Context) error,
+	fc *FunctionalComponent,
 ) Component {
-	return &FunctionalComponent{
-		init, start, stop,
-	}
+	return fc
 }
 
-func (fc *FunctionalComponent) Init(ctx context.Context) error  { return fc.init(ctx) }
-func (fc *FunctionalComponent) Start(ctx context.Context) error { return fc.start(ctx) }
-func (fc *FunctionalComponent) Stop(ctx context.Context) error  { return fc.stop(ctx) }
+func (fc *FunctionalComponent) Init(ctx context.Context) error {
+	if fc.init != nil {
+		return fc.init(ctx)
+	}
+	return nil
+}
+func (fc *FunctionalComponent) Start(ctx context.Context) error {
+	if fc.start != nil {
+		return fc.start(ctx)
+	}
+	return nil
+}
+func (fc *FunctionalComponent) Stop(ctx context.Context) error {
+	if fc.stop != nil {
+		return fc.stop(ctx)
+	}
+	return nil
+}