R: add service bindings example

examples/service-bindings/.gitignore

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+dist

examples/service-bindings/Makefile

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+.PHONY: dev
+dev:
+	wrangler dev
+
+.PHONY: build
+build:
+	mkdir -p dist
+	tinygo build -o ./dist/app.wasm -target wasm ./...
+
+.PHONY: publish
+publish:
+	wrangler publish

examples/service-bindings/README.md

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+# service-bindings
+
+- Service bindings are an API that facilitate Worker-to-Worker communication via explicit bindings defined in your configuration.
+- In this example, invoke [hello](https://github.com/syumai/workers/tree/main/examples/hello) using Service bindings.
+
+## Development
+
+### Requirements
+
+This project requires these tools to be installed globally.
+
+* wrangler
+* tinygo
+
+### Deploy Steps
+
+1. Deploy [hello](https://github.com/syumai/workers/tree/main/examples/hello) first.
+2. Define service bindings in `wrangler.toml`.
+    ```toml
+    services = [
+        { binding = "hello", service = "hello" }
+    ]
+    ```
+3. Deploy this example.
+    ```
+    make build   # build Go Wasm binary
+    make publish # publish worker
+    ```
+
+## Documents
+
+- https://developers.cloudflare.com/workers/runtime-apis/service-bindings/

examples/service-bindings/go.mod

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+module github.com/syumai/fetch
+
+go 1.18
+
+require github.com/syumai/workers v0.0.0
+
+replace github.com/syumai/workers => ../../

examples/service-bindings/go.sum

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+github.com/syumai/workers v0.1.0 h1:z5QfQR2X+PCKzom7RodpI5J4D5YF7NT7Qwzb9AM9dgY=
+github.com/syumai/workers v0.1.0/go.mod h1:alXIDhTyeTwSzh0ZgQ3cb9HQPyyYfIejupE4Z3efr14=

examples/service-bindings/main.go

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+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/syumai/workers"
+	"github.com/syumai/workers/cloudflare"
+	"github.com/syumai/workers/cloudflare/fetch"
+)
+
+func main() {
+	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		ctx := req.Context()
+
+		obj := cloudflare.GetBinding(ctx, "hello")
+		cli := fetch.NewClient(fetch.WithBinding(obj))
+		r, err := fetch.NewRequest(ctx, http.MethodGet, req.URL.String(), nil)
+		if err != nil {
+			fmt.Println(err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+
+		res, err := cli.Do(r)
+		if err != nil {
+			fmt.Println(err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+
+		io.Copy(w, res.Body)
+	})
+	workers.Serve(handler)
+}

examples/service-bindings/worker.mjs

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+import "../assets/polyfill_performance.js";
+import "../assets/wasm_exec.js";
+import mod from "./dist/app.wasm";
+
+const go = new Go();
+
+const readyPromise = new Promise((resolve) => {
+  globalThis.ready = resolve;
+});
+
+const load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
+  go.run(instance);
+  return instance;
+});
+
+export default {
+  async fetch(req, env, ctx) {
+    await load;
+    await readyPromise;
+    return handleRequest(req, { env, ctx });
+  }
+}

examples/service-bindings/wrangler.toml

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+name = "service-bindings"
+main = "./worker.mjs"
+compatibility_date = "2023-02-24"
+services = [
+    { binding = "hello", service = "hello" }
+]
+
+[build]
+command = "make build"