add node 14 async-local-storage dev example

dev/async-local-storage.js

@@ -0,0 +1,49 @@
+"use strict";
+
+/**
+ * Testing the new AsyncLocalStorage module
+ * to store the current context in the action into the async local storage.
+ *
+ * Please note it works only >= Node 14.
+ */
+
+const  ServiceBroker = require("../src/service-broker");
+const { AsyncLocalStorage } = require("async_hooks");
+
+const asyncLocalStorage = new AsyncLocalStorage();
+
+const AsyncLocalStorageMiddleware = {
+	localAction(handler) {
+		return (ctx) => asyncLocalStorage.run(ctx, () => handler(ctx));
+	},
+};
+
+// Create broker
+const broker = new ServiceBroker({
+	middlewares: [AsyncLocalStorageMiddleware]
+});
+
+broker.createService({
+	name: "greeter",
+	actions: {
+		hello: {
+			async handler(ctx) {
+				await this.doSomething();
+				return `Hello ${ctx.params.name}`;
+			}
+		}
+	},
+	methods: {
+		async doSomething() {
+			await Promise.resolve().delay(500);
+			const ctx = asyncLocalStorage.getStore();
+			console.log("Current context params:", ctx ? ctx.params : "<No context>");
+		}
+	}
+});
+
+broker.start()
+	.then(() => broker.call("greeter.hello", { name: "Moleculer" }))
+	.then(res => broker.logger.info("Result:", res))
+	.catch(err => broker.logger.error(err))
+	.then(() => broker.stop());