I'm trying to use cluster in serverless offline. but after running serverless offline it gives me following error

offline: Failure: offline: handler 'handler' in /home/Documents/cluster is not a function
Error: offline: handler 'handler' in /home/Documents/cluster is not a function
    at InProcessRunner.run (/home/Documents/node_modules/serverless-offline/dist/lambda/handler-runner/in-process-runner/InProcessRunner.js:160:13)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async LambdaFunction.runHandler (/home/Documents/node_modules/serverless-offline/dist/lambda/LambdaFunction.js:368:20)
    at async hapiHandler (/home/Documents/node_modules/serverless-offline/dist/events/http/HttpServer.js:702:18)
    at async exports.Manager.execute (/home/Documents/node_modules/@hapi/hapi/lib/toolkit.js:60:28)
    at async Object.internals.handler (/home/Documents/node_modules/@hapi/hapi/lib/handler.js:46:20)
    at async exports.execute (/home/Documents/node_modules/@hapi/hapi/lib/handler.js:31:20)
    at async Request._lifecycle (/home/Documents/node_modules/@hapi/hapi/lib/request.js:371:32)
    at async Request._execute (/home/Documents/node_modules/@hapi/hapi/lib/request.js:281:9)

and after that it start to kill process. I don't have any idea how to implement cluster in serverless offline.

if I'm call serverless handler in master process it works file for single thread but not for child process.

const cluster = require("cluster");
const totalCPUs = require("os").cpus().length;
const serverless = require("serverless-http");
const app = require("./api");

console.log("cluster.isMaster", cluster.isMaster);
if (cluster.isMaster) {
  console.log(`Number of CPUs is ${totalCPUs}`);
  console.log(`Master ${process.pid} is running`);

  // Fork workers.
  for (let i = 0; i < totalCPUs; i++) {
    cluster.fork();
  }
  module.exports.handler = serverless(app);// if I declare here it works fine 
  cluster.on("exit", (worker, code, signal) => {
    // console.log(`process killed:`, worker.kill());
    console.log(`${worker.process.pid} is killed`);
    // console.log("code, signal ", code, signal);
    // cluster.fork();
    console.log(`new proccess pid: ${process.pid}`);
  });
} else {
  console.log("process pid ", process.pid);
  // console.log("serverless(app)",app);
  // runServer.runServer();
  module.exports.handler = serverless(app);// if I declare here never get called and 
                                          //kill all process
}

please guide, I'm frustrate to implement this because I'm doing this from long time but not getting any solution.