test: change anonymous function to arrow function

PR-URL: nodejs#24528
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

test/parallel/test-http-client-timeout-agent.js

@@ -32,7 +32,7 @@ const options = {
   host: '127.0.0.1',
 };
 
-const server = http.createServer(function(req, res) {
+const server = http.createServer((req, res) => {
   const m = /\/(.*)/.exec(req.url);
   const reqid = parseInt(m[1], 10);
   if (reqid % 2) {
@@ -51,7 +51,7 @@ server.listen(0, options.host, function() {
     options.path = `/${requests_sent}`;
     const req = http.request(options);
     req.id = requests_sent;
-    req.on('response', function(res) {
+    req.on('response', (res) => {
       res.on('data', function(data) {
         console.log(`res#${this.req.id} data:${data}`);
       });
@@ -78,7 +78,7 @@ server.listen(0, options.host, function() {
 
   setTimeout(function maybeDone() {
     if (requests_done >= requests_sent) {
-      setTimeout(function() {
+      setTimeout(() => {
         server.close();
       }, 100);
     } else {
@@ -87,7 +87,7 @@ server.listen(0, options.host, function() {
   }, 100);
 });
 
-process.on('exit', function() {
+process.on('exit', () => {
   console.error(`done=${requests_done} sent=${requests_sent}`);
   // check that timeout on http request was not called too much
   assert.strictEqual(requests_done, requests_sent);