add kv-counter example

examples/kv-counter/.gitignore

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+dist

examples/kv-counter/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/kv-counter/README.md

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+# kv-counter
+
+* This app counts page view using Cloudflare KV.
+
+## Demo
+
+* https://kv-counter.syumai.workers.dev/
+
+## Development
+
+### Requirements
+
+This project requires these tools to be installed globally.
+
+* wrangler
+* tinygo
+
+### Commands
+
+```
+make dev     # run dev server
+make build   # build Go Wasm binary
+make publish # publish worker
+```
+
+## Author
+
+syumai
+
+## License
+
+MIT

examples/kv-counter/go.mod

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+module github.com/syumai/workers/examples/kv-counter
+
+go 1.18
+
+require github.com/syumai/workers v0.0.0
+
+replace github.com/syumai/workers => ../../

examples/kv-counter/main.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+
+	"github.com/syumai/workers"
+)
+
+// counterNamespace is a bounded KV namespace for storing counter.
+const counterNamespace = "COUNTER"
+
+// countKey is a key to store current count value to the KV namespace.
+const countKey = "count"
+
+func handleErr(w http.ResponseWriter, msg string, err error) {
+	log.Println(err)
+	w.WriteHeader(http.StatusInternalServerError)
+	w.Write([]byte(msg))
+}
+
+func main() {
+	// initialize KV namespace instance
+	kv, err := workers.NewKVNamespace(counterNamespace)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to init KV: %v", err)
+		os.Exit(1)
+	}
+
+	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
+		if req.URL.Path != "/" {
+			w.WriteHeader(http.StatusNotFound)
+			return
+		}
+
+		countStr, err := kv.GetString(countKey, nil)
+		if err != nil {
+			handleErr(w, "failed to get current count\n", err)
+			return
+		}
+
+		/*
+			countReader, err := kv.GetReader(countKey, nil)
+			if err != nil {
+				handleErr(w, "failed to get current count\n", err)
+				return
+			}
+			b, _ := io.ReadAll(countReader)
+			countStr := string(b)
+		*/
+
+		// ignore err and treat count value as 0
+		count, _ := strconv.Atoi(countStr)
+
+		nextCountStr := strconv.Itoa(count + 1)
+
+		err = kv.PutString(countKey, nextCountStr, nil)
+		if err != nil {
+			handleErr(w, "failed to put next count\n", err)
+			return
+		}
+
+		/*
+			err = kv.PutReader(countKey, strings.NewReader(nextCountStr), nil)
+			if err != nil {
+				handleErr(w, "failed to put next count\n", err)
+				return
+			}
+		*/
+
+		w.Header().Set("Content-Type", "text/plain")
+
+		/*
+			// List returns only `count` as the keys in this namespace.
+			v, err := kv.List(nil)
+			if err != nil {
+				handleErr(w, "failed to list\n", err)
+				return
+			}
+			for i, key := range v.Keys {
+				fmt.Fprintf(w, "%d: %s\n", i, key.Name)
+			}
+		*/
+
+		w.Write([]byte(nextCountStr))
+	})
+
+	workers.Serve(nil)
+}

examples/kv-counter/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 load = WebAssembly.instantiate(mod, go.importObject).then((instance) => {
+  go.run(instance);
+  return instance;
+});
+
+async function processRequest(event) {
+  const req = event.request;
+  await load;
+  return handleRequest(req);
+}
+
+addEventListener("fetch", (event) => {
+  event.respondWith(processRequest(event));
+})

examples/kv-counter/wrangler.toml

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+name = "kv-counter"
+main = "./worker.mjs"
+compatibility_date = "2022-05-13"
+compatibility_flags = [
+    "streams_enable_constructors"
+]
+
+[[kv_namespaces]]
+binding = "COUNTER"
+id = "fe0ef36853f04fe986c1ade5271ea6a4"
+preview_id = "916f05d37f4741e0a19aa3d0bd4d282e"
+
+[build]
+command = "make build"