Fix node cluster for express (#7504)

frameworks/JavaScript/express/app.js

@@ -9,14 +9,17 @@ const cluster = require('cluster'),
 
 const bodyParser = require('body-parser');
 
-if (cluster.isMaster) {
+if (cluster.isPrimary) {
+  console.log(`Primary ${process.pid} is running`);
+
   // Fork workers.
   for (let i = 0; i < numCPUs; i++) {
     cluster.fork();
   }
 
-  cluster.on('exit', (worker, code, signal) =>
-    console.log('worker ' + worker.pid + ' died'));
+  cluster.on('exit', (worker, code, signal) => {
+    console.log(`worker ${worker.process.pid} died`);
+  });
 } else {
   const app = module.exports = express();