Add express demo from oven-sh/bun#3775 (comment)

app.ts

@@ -1 +1,16 @@
-console.log("Hello via Bun!");
+import express from "express";
+
+const PORT = parseInt(process.env.PORT || "8080");
+const app = express();
+
+function getRandomNumber(min: number, max: number) {
+  return Math.floor(Math.random() * (max - min) + min);
+}
+
+app.get("/rolldice", (req, res) => {
+  res.send(getRandomNumber(1, 6).toString());
+});
+
+app.listen(PORT, () => {
+  console.log(`Listening for requests on http://localhost:${PORT}`);
+});

instrumentation.ts

@@ -0,0 +1,18 @@
+// Require dependencies
+import { NodeSDK } from "@opentelemetry/sdk-node";
+import { ConsoleSpanExporter } from "@opentelemetry/sdk-trace-node";
+import { getNodeAutoInstrumentations } from "@opentelemetry/auto-instrumentations-node";
+import {
+  PeriodicExportingMetricReader,
+  ConsoleMetricExporter,
+} from "@opentelemetry/sdk-metrics";
+
+const sdk = new NodeSDK({
+  traceExporter: new ConsoleSpanExporter(),
+  metricReader: new PeriodicExportingMetricReader({
+    exporter: new ConsoleMetricExporter(),
+  }),
+  instrumentations: [getNodeAutoInstrumentations()],
+});
+
+sdk.start();

package.json

@@ -2,10 +2,20 @@
   "name": "otel-auto-bun-repro",
   "module": "app.ts",
   "type": "module",
+  "scripts": {
+    "start": "bun run --preload ./instrumentation.ts  ./app.ts"
+  },
   "devDependencies": {
     "@types/bun": "latest"
   },
   "peerDependencies": {
     "typescript": "^5.0.0"
+  },
+  "dependencies": {
+    "@opentelemetry/auto-instrumentations-node": "^0.41.0",
+    "@opentelemetry/sdk-metrics": "^1.21.0",
+    "@opentelemetry/sdk-node": "^0.48.0",
+    "@opentelemetry/sdk-trace-node": "^1.21.0",
+    "express": "^4.18.2"
   }
-}
+}