问为什么NodeJs集群模块不能工作？

EN

import cluster from "cluster";
import { cpus } from "os";

import dotenv from "dotenv";
dotenv.config();

import express, { Express } from "express";
import log from "./logger";
import database from "./database";
import router from "./router";

const app: Express = express();

// Middleware
app.use(express.json());
app.use(express.urlencoded({ extended: false }));

const port = <number>(<unknown>process.env.PORT);
const host = <string>process.env.HOST;

const numCPU = cpus().length;
if (cluster.isPrimary) {
   for (let i = 0; i < numCPU; i++) {
      cluster.fork();
   }

   cluster.on("listening", (worker) => {
      // Not printing anything
      console.log(worker.process.pid);
   });

   cluster.on("exit", (worker, code, signal) => {
      log.error(`Worker ${worker.process.pid} died. Starting a new worker...`);
      cluster.fork();
   });
} else {
   app.listen(port, host, () => {
      // Only prints this once.
      log.info(`Server ${process.pid} listening at http://${host}:${port}`);
      database();
      router(app);
   });
}