diff --git a/examples/r2-image-server/Makefile b/examples/r2-image-server/Makefile
index c9d7430..320ddc3 100644
--- a/examples/r2-image-server/Makefile
+++ b/examples/r2-image-server/Makefile
@@ -5,7 +5,7 @@ dev:
 .PHONY: build
 build:
 	mkdir -p dist
-	tinygo build -o ./dist/app.wasm -target wasm ./main.go
+	tinygo build -o ./dist/app.wasm -target wasm ./...
 
 .PHONY: publish
 publish:
diff --git a/examples/r2-image-server/jsutil.go b/examples/r2-image-server/jsutil.go
index 5edeb77..fe871c1 100644
--- a/examples/r2-image-server/jsutil.go
+++ b/examples/r2-image-server/jsutil.go
@@ -29,6 +29,8 @@ func newPromise(fn js.Func) js.Value {
 }
 
 func awaitPromise(promiseVal js.Value) (js.Value, error) {
+	fmt.Println("await promise")
+	fmt.Println(promiseVal.Call("toString").String())
 	resultCh := make(chan js.Value)
 	errCh := make(chan error)
 	var then, catch js.Func
@@ -47,8 +49,10 @@ func awaitPromise(promiseVal js.Value) (js.Value, error) {
 	promiseVal.Call("then", then).Call("catch", catch)
 	select {
 	case result := <-resultCh:
+		fmt.Println("got result of promise")
 		return result, nil
 	case err := <-errCh:
+		fmt.Println("got error of promise")
 		return js.Value{}, err
 	}
 }
diff --git a/examples/r2-image-server/main.go b/examples/r2-image-server/main.go
index f03f942..d4d70bc 100644
--- a/examples/r2-image-server/main.go
+++ b/examples/r2-image-server/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"io"
+	"log"
 	"net/http"
 
 	"github.com/syumai/workers"
@@ -11,7 +12,8 @@ import (
 // bucketName is R2 bucket name defined in wrangler.toml.
 const bucketName = "BUCKET"
 
-func handleErr(w http.ResponseWriter, msg string) {
+func handleErr(w http.ResponseWriter, msg string, err error) {
+	log.Println(err)
 	w.WriteHeader(http.StatusInternalServerError)
 	w.Write([]byte(msg))
 }
@@ -19,15 +21,17 @@ func handleErr(w http.ResponseWriter, msg string) {
 // This example is based on implementation in syumai/workers-playground
 // * https://github.com/syumai/workers-playground/blob/e32881648ccc055e3690a0d9c750a834261c333e/r2-image-viewer/src/index.ts#L30
 func handler(w http.ResponseWriter, req *http.Request) {
+	fmt.Println("new R2Bucket")
 	bucket, err := NewR2Bucket(bucketName)
 	if err != nil {
-		handleErr(w, "failed to get R2Bucket\n")
+		handleErr(w, "failed to get R2Bucket\n", err)
 		return
 	}
 	imgPath := req.URL.Path
+	fmt.Println("bucket.get")
 	imgObj, err := bucket.Get(imgPath)
 	if err != nil {
-		handleErr(w, "failed to get R2Object\n")
+		handleErr(w, "failed to get R2Object\n", err)
 		return
 	}
 	w.Header().Set("Cache-Control", "public, max-age=14400")
@@ -37,6 +41,7 @@ func handler(w http.ResponseWriter, req *http.Request) {
 		contentType = *imgObj.HTTPMetadata.ContentType
 	}
 	w.Header().Set("Content-Type", contentType)
+	fmt.Println("return result")
 	io.Copy(w, imgObj.Body)
 }
 
diff --git a/examples/r2-image-server/r2bucket.go b/examples/r2-image-server/r2bucket.go
index 171f522..96511b0 100644
--- a/examples/r2-image-server/r2bucket.go
+++ b/examples/r2-image-server/r2bucket.go
@@ -41,6 +41,7 @@ func (r *r2Bucket) Get(key string) (*R2Object, error) {
 	if err != nil {
 		return nil, err
 	}
+	fmt.Println(v)
 	if v.IsNull() {
 		return nil, nil
 	}
diff --git a/examples/r2-image-server/r2object.go b/examples/r2-image-server/r2object.go
index 26e97b1..9403f6d 100644
--- a/examples/r2-image-server/r2object.go
+++ b/examples/r2-image-server/r2object.go
@@ -41,6 +41,7 @@ func (o *R2Object) BodyUsed() (bool, error) {
 // toR2Object converts JavaScript side's R2Object to *R2Object.
 // * https://github.com/cloudflare/workers-types/blob/3012f263fb1239825e5f0061b267c8650d01b717/index.d.ts#L1094
 func toR2Object(v js.Value) (*R2Object, error) {
+	fmt.Println("toR2Object")
 	uploaded, err := dateToTime(v.Get("uploaded"))
 	if err != nil {
 		return nil, fmt.Errorf("error converting uploaded: %w", err)
diff --git a/examples/r2-image-server/worker.mjs b/examples/r2-image-server/worker.mjs
index a0bb726..06ce572 100644
--- a/examples/r2-image-server/worker.mjs
+++ b/examples/r2-image-server/worker.mjs
@@ -9,9 +9,11 @@ const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
   return instance;
 });
 
-export default {
-  async fetch(req) {
-    await load;
-    return handleRequest(req);
-  },
-};
+async function processRequest(event) {
+  const req = event.request;
+  await load;
+  console.log("finished loading");
+  return handleRequest(req);
+}
+
+addEventListener("fetch", (event) => event.respondWith(processRequest(event)))