Is it possible to send a GET request to a puppeteer script?

I am creating a React site that retrieves web-scraping data from a third-party site. My puppeteer script runs fine as a .js file, but when I add it to my server using Express & Axios, it seemingly does not go to the page and cannot execute the following lines of code. (My code is a lot longer so I put a shorter example here:)

puppeteer.js // works fine

const puppeter = require('puppeteer'); 

(async () => {


    const browser = await puppeter.launch({headless: true});
    const page = await browser.newPage();
    await page.goto(`https://www.scrapethissite.com/lessons/`);

    let header = "";

    header = await page.$eval( "#header", el => el.textContent.trim());

    console.log(header)
  

    await browser.close(); 
    

})();

index.js // does not work

const puppeteer = require('puppeteer'); 
app.get('/', async (req, res) => {
 const browser = await puppeter.launch({headless: true});
    const page = await browser.newPage();
    await page.goto(`https://www.scrapethissite.com/lessons/`);

    let header = "";

    header = await page.$eval( "#header", el => el.textContent.trim());

    console.log(header)
  

    await browser.close(); 
});

The server code either outputs the header in the console as ” ” or when I modify it slightly to remove the initialization of the variable “header” and just have the line: let header = await page.$eval( "#header", el => el.textContent.trim()); I get an “UnhandledPromiseRejectionWarning.” The script works fine by itself, but when I use it in the server I start to get errors. Is this a problem with using Puppeteer in Axios or do I need to modify my code so it can handle the promises better?