asyncRepl.js

const vm = require('vm');
const repl = require('repl');

function myEval(cmd, context, filename, callback) {
  let result;
  try {
    result = vm.runInContext(cmd, context);
  } catch (e) {
    return callback(e);
  }

  if(result.then) {
    result
      .then((result) => callback(null, result))
      .catch((err) => callback(err))
  } else {
    callback(null, result);
  }
}

repl.start({prompt: '> ', eval: myEval});