[docs] update resource initialization (#2844)

* [docs] update resource initialization

* Formatting

* [docs] handle error case in resource merge

* Update manual.md

Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

website_docs/manual.md

@@ -46,15 +46,22 @@ func newExporter(ctx context.Context)  /* (someExporter.Exporter, error) */ {
 }
 
 func newTraceProvider(exp sdktrace.SpanExporter) *sdktrace.TracerProvider {
-    // The service.name attribute is required.
-	resource := resource.NewWithAttributes(
-		semconv.SchemaURL,
-		semconv.ServiceNameKey.String("ExampleService"),
+	// Ensure default SDK resources and the required service name are set.
+	r, err := resource.Merge(
+		resource.Default(),
+		resource.NewWithAttributes(
+			semconv.SchemaURL,
+			semconv.ServiceNameKey.String("ExampleService"),
+		)
 	)
+
+	if err != nil {
+		panic(err)
+	}
 
 	return sdktrace.NewTracerProvider(
 		sdktrace.WithBatcher(exp),
-		sdktrace.WithResource(resource),
+		sdktrace.WithResource(r),
 	)
 }