How once having created object of the browser it is constant to address it?

Question

Node.js

Hello.

I have the following in stock:

const express = require('express')
const puppeteer = require('puppeteer');
const app = express()
const port = 3000


app.get('/render', (req, res) => {
    (async (req) => {
        const browser = await puppeteer.launch();
        const page = await browser.newPage();
        await page.goto(req.query.url, {waitUntil: 'networkidle2'});
        await page.emulateMediaType('screen')
        await page.setViewport({
            width: 400,
            height: 1080,
            deviceScaleFactor: 1,
        });
        console.log(req.query.url)
        await page.pdf({
            path: 'hn.pdf',
            format: 'A4',
            margin: {
                top: 15,
                bottom: 15,
                right: 15,
                left: 15
            }
        });
        console.log('rendered')

        await browser.close();
    })(req)

    res.send('123')
})

app.listen(port, () => {
    console.log(`Example app listening at http://localhost:${port}`)
})

I want to speed up rendering by not creating a browser object for each request, but using it as a resource cached in RAM.

Moving the creation of the browser object behind the /render handler results in a TypeError: browser.newPage is not a function
Tell me what to do?

PS don't kick too hard, I don't really understand how to use all the features of node.js