Websocket is not defined error

import * as trpcExpress from "@trpc/server/adapters/express";
import { applyWSSHandler } from "@trpc/server/adapters/ws";
import express from "express";
import cors from "cors";
import { appRouter } from "./routers/_app";
import { createContext } from "./context";
import ws from 'ws'

const app = express();
app.use(cors({ origin: ["http://localhost:3000", "http://localhost:3001"] }));
app.use(
    "/trpc",
    trpcExpress.createExpressMiddleware({
        router: appRouter,
        createContext,
    })
);

const server = app.listen(8000);

applyWSSHandler({
    wss: new ws.Server({ server }),
    router: appRouter,
    createContext
})

import { inferAsyncReturnType } from "@trpc/server";
import * as trpcExpress from "@trpc/server/adapters/express";
import { NodeHTTPCreateContextFnOptions } from '@trpc/server/adapters/node-http';
import { IncomingMessage } from 'http';
import ws from 'ws';

export const createContext = ({ req, res }: trpcExpress.CreateExpressContextOptions |  NodeHTTPCreateContextFnOptions<IncomingMessage, ws>) => {
    return ({
        req, res
    })
}
export type Context = inferAsyncReturnType<typeof createContext>;