How to use output from npm simple-ssh exec command outside of the command itself?

Question

I am trying to implement a new feature for our in-house brand of hubot. The feature uses the npm package simple-ssh (wrapper for ssh2) and basically takes an environment (i.e. "@hubot get versions DEV) as input, gets the servers and credentials for that environment, and runs a number of bash commands to return a version for a particular software on each server.

I am able to run this fine and view the output when using console.log(), but what I need is to append to an array so I can send it back in the hubot reply. However, I can append to neither the response string nor the array I have created from within the out(stdout) function after each .exec.

How can I use the stdout from each command in my reply with hubot?

require('dotenv').config('../.env');

const SSH = require('simple-ssh');
const { Resolver } = require('../../../utils/Resolver');

const resolver = new Resolver();
let response = '';
let versions = [];

// parses initial request from flowdock into separate environments
function getEnvsFromRequest(reqEnvsStr) {
  return reqEnvsStr.toUpperCase().replace(/AND/, '').replace(/\s+/g, '').split(',');
}

function getVersions(res) {
  const env = getEnvsFromRequest(res.match[2].toString());
  const resEnv = resolver.resolveEnv(env);
  if (resEnv === null) {
    res.reply(`${env} is not in my list of available environments.`);
    return;
  }
  if (resEnv.length > 0) {
    response = response.concat(`\nHere are the results for ${resEnv}:\n`);
    response = response.concat('------------------------\n');
  }
// Resolve hosts for environment
  let resHosts = [];
  resHosts = resolver.resolveHosts(resEnv);
// Resolve creds for environment
  let resCreds = [];
  resCreds = resolver.resolveCreds(resEnv);

// Loop through available hosts for each environment
  resHosts.forEach((resHost) => {
    dummy = [];
    dummy.push(`${resHost}:\n`);
    const ssh = new SSH({
      host: resHost,
      user: resCreds[0],
      pass: resCreds[1],
    });

    ssh
    // Example 1 version
      .exec('head -3 /app/foo/foo/bar | tail -1 | cut -d \'=\' -f 2', {
        // out(stdout) { response.concat(`Foo foo bar version: ${stdout}`); },
        out(stdout) { dummy.push(`Foo foo bar version: ${stdout}`); },
      })
    // Example 2 version
      .exec('cd /app/foo/bar && ls -td -- * | head -n 1', {
        // out(stdout) { response.concat(`Foo bar version: ${stdout}`); },
        out(stdout) { dummy.push(`Foo bar version: ${stdout}`); },
      })
      .start();
  });
  versions.push(dummy)
}
response.concat(versions.toString());
res.reply(response);