test: replace anonymous function with arrow function

PR-URL: #24529
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

test/parallel/test-child-process-fork-dgram.js

@@ -38,10 +38,10 @@ const assert = require('assert');
 if (process.argv[2] === 'child') {
   let childServer;
 
-  process.once('message', function(msg, clusterServer) {
+  process.once('message', (msg, clusterServer) => {
     childServer = clusterServer;
 
-    childServer.once('message', function() {
+    childServer.once('message', () => {
       process.send('gotMessage');
       childServer.close();
     });
@@ -59,15 +59,15 @@ if (process.argv[2] === 'child') {
   let childGotMessage = false;
   let parentGotMessage = false;
 
-  parentServer.once('message', function(msg, rinfo) {
+  parentServer.once('message', (msg, rinfo) => {
     parentGotMessage = true;
     parentServer.close();
   });
 
-  parentServer.on('listening', function() {
+  parentServer.on('listening', () => {
     child.send('server', parentServer);
 
-    child.on('message', function(msg) {
+    child.on('message', (msg) => {
       if (msg === 'gotMessage') {
         childGotMessage = true;
       } else if (msg = 'handlReceived') {
@@ -79,7 +79,7 @@ if (process.argv[2] === 'child') {
   function sendMessages() {
     const serverPort = parentServer.address().port;
 
-    const timer = setInterval(function() {
+    const timer = setInterval(() => {
       /*
        * Both the parent and the child got at least one message,
        * test passed, clean up everything.
@@ -94,7 +94,7 @@ if (process.argv[2] === 'child') {
           msg.length,
           serverPort,
           '127.0.0.1',
-          function(err) {
+          (err) => {
             assert.ifError(err);
           }
         );
@@ -104,7 +104,7 @@ if (process.argv[2] === 'child') {
 
   parentServer.bind(0, '127.0.0.1');
 
-  process.once('exit', function() {
+  process.once('exit', () => {
     assert(parentGotMessage);
     assert(childGotMessage);
   });