Add express example

examples/package.json

@@ -1,7 +1,8 @@
 {
   "dependencies": {
-    "@azure/app-configuration-provider": "latest",
+    "@azure/app-configuration-provider": "2.0.0-preview.2",
     "@azure/identity": "^4.1.0",
-    "dotenv": "^16.3.1"
+    "dotenv": "^16.3.1",
+    "express": "^4.21.2"
   }
 }

examples/server.mjs

@@ -0,0 +1,48 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+import * as dotenv from "dotenv";
+dotenv.config()
+
+import { load } from "@azure/app-configuration-provider";
+const connectionString = process.env.APPCONFIG_CONNECTION_STRING;
+const appConfig = await load(connectionString, {
+    refreshOptions: {
+        enabled: true,
+        refreshIntervalInMs: 5_000
+    }
+});
+
+appConfig.onRefresh(() => {
+    console.log("Configuration has been refreshed.");
+});
+
+import express from "express";
+
+const server = express();
+const PORT = 3000;
+
+server.use(express.json());
+
+// Use a middleware to achieve request-driven configuration refresh
+server.use((req, res, next) => {
+    // this call s not blocking, the configuration will be updated asynchronously
+    appConfig.refresh();
+    next();
+});
+
+server.get("/", (req, res) => {
+    res.send("Please go to /config to get the configuration.");
+});
+
+server.get("/config", (req, res) => {
+    res.json(appConfig.constructConfigurationObject());
+});
+
+server.get("/config/:key", (req, res) => {
+    res.json(appConfig.get(req.params.key) ?? "");
+});
+
+server.listen(PORT, () => {
+  console.log(`Server is running on http://localhost:${PORT}`);
+});