I am trying get specific string from email body and return it. Inside simpleParser function I assign output of substring to token variable which I declare earlier. Why when I print token in getEmails function I get empty string and in simpleParse I get string with value that I wanted?

const Imap = require('imap');
const {simpleParser} = require('mailparser');
const imapConfig = {
  user: '',
  password: '',
  host: 'imap.gmail.com',
  port: 993,
  tls: true,
  tlsOptions: {
    rejectUnauthorized: false
  }
};

let token = "";

async function getEmails() {
  try {
    const imap = new Imap(imapConfig);
     imap.once('ready', () => {
      imap.openBox('INBOX', false, () => {
        imap.search(['UNSEEN'], (err, results) => {
          const f = imap.fetch(results, {bodies: ''});
          f.on('message', msg => {
            msg.on('body', stream => {
              simpleParser(stream, async (err, parsed) => {
                // const {from, subject, textAsHtml, text} = parsed;
                // console.log(parsed);
                let tokenNr = parsed.html.search('token');
                token = parsed.html.substring(tokenNr+6, tokenNr+66);
                console.log(token);
              });
            });
          });
          f.once('error', ex => {
            return Promise.reject(ex);
          });
          f.once('end', () => {
            console.log('Done fetching all messages!');
            imap.end();
          });
        });
      });
    });

    imap.once('error', err => {
      console.log(err);
    });

    imap.once('end', () => {
      console.log('Connection ended');
    });

    imap.connect();
  } catch (ex) {
    console.log('an error occurred');
  }
  console.log(token);
  return token;
};