There is an option to save user data using the userDataDir option when launching puppeteer. This stores the session and other things related to launching chrome.

puppeteer.launch({
  userDataDir: "./user_data"
});

It doesn't go into great detail but here's a link to the docs for it: https://pptr.dev/#?product=Puppeteer&version=v1.6.1&show=api-puppeteerlaunchoptions

In puppeter you have access to the session cookies through page.cookies().

So once you log in, you could get every cookie and save it in a json file:

const fs = require(fs);
const cookiesFilePath = 'cookies.json';
// Save Session Cookies
const cookiesObject = await page.cookies()
// Write cookies to temp file to be used in other profile pages
fs.writeFile(cookiesFilePath, JSON.stringify(cookiesObject),
 function(err) { 
  if (err) {
  console.log('The file could not be written.', err)
  }
  console.log('Session has been successfully saved')
})

Then, on your next iteration right before using page.goto() you can call page.setCookie() to load the cookies from the file one by one:

const previousSession = fs.existsSync(cookiesFilePath)
if (previousSession) {
  // If file exist load the cookies
  const cookiesString = fs.readFileSync(cookiesFilePath);
  const parsedCookies = JSON.parse(cookiesString);
  if (parsedCookies.length !== 0) {
    for (let cookie of parsedCookies) {
      await page.setCookie(cookie)
    }
    console.log('Session has been loaded in the browser')
  }
}

Checkout the docs:

• https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagecookiesurls
• https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md#pagesetcookiecookies

For a version of the above solution that actually works and doesn't rely on jsonfile (instead using the more standard fs) check this out:

Setup:

const fs = require('fs');
const cookiesPath = "cookies.txt";

Reading the cookies (put this code first):

// If the cookies file exists, read the cookies.
const previousSession = fs.existsSync(cookiesPath)
if (previousSession) {
  const content = fs.readFileSync(cookiesPath);
  const cookiesArr = JSON.parse(content);
  if (cookiesArr.length !== 0) {
    for (let cookie of cookiesArr) {
      await page.setCookie(cookie)
    }
    console.log('Session has been loaded in the browser')
  }
}

Writing the cookies:

// Write Cookies
const cookiesObject = await page.cookies()
fs.writeFileSync(cookiesPath, JSON.stringify(cookiesObject));
console.log('Session has been saved to ' + cookiesPath);