Micro Dev hangs

index.ts

import { createTransport, SendMailOptions } from 'nodemailer';
import { IncomingMessage, ServerResponse } from 'http'
import { json, send } from 'micro';


type MicroFunction = (req: IncomingMessage, res: ServerResponse) => string | void | Promise<any>;

type DorianMailData = {
  dest: string,
  body: string,
  subject?: string,
  from?: string
};

type CleanMailData = {
  dest: string,
  body: string,
  subject: string,
  from: string
};

type DataCleaner = (md: DorianMailData) => CleanMailData;

type SendErrorMsg = (res: ServerResponse, msg: string) => void | Promise<void>;


const defaultSubject = '';
const defaultFrom = 'Dorian Bot <do-not-reply@dorianbusiness.com>';

const mailer = createTransport({
  host: process.env.MAILER_HOST,
  secure: false,
  port: 25,
  auth: {
    user: process.env.MAILER_USER,
    pass: process.env.MAILER_PASS
  }
});


const fillDefaults: DataCleaner = md =>
  Object.assign({}, md, { from: md.from || defaultFrom, subject: md.subject || defaultSubject });

const sendMail = async (md: CleanMailData) => await mailer
  .sendMail({
    from: md.from,
    subject: md.subject,
    text: md.body,
    to: md.dest,
    headers: {
      'Return-Path': md.from,
      'ReturnPath': md.from
    }
  });

const send400Err: SendErrorMsg = async (res, msg) => send(res, 400, { error: msg });

// TODO instead of console.error, use winston or another logging library.
const waitForEmail: MicroFunction = async (req, res) => {
  
  // VERIFY (do we need to do this?)
  try {
    await mailer.verify();
  } catch(er) {
    console.error('MAILER NOT VERIFIED');
    return await send400Err(res, 'Could not establish initial connection to mail server.');
  }

  console.log('Verified');
  
  // PARSE
  let data: { to?: string, body?: string, subject?: string, from?: string } = null;
  try {
    console.log('Grabbing json...');
    data = await json(req);
    console.log('JSON got!');
  } catch(err) {
    console.error('Request didn\'t have data');
    return await send400Err(res, 'No json data in the request body was found.');
  }
  
  // VALIDATE data
  if(!data.to || !data.body) {
    console.error('Request data invalid. Need to and body fields');
    return await send400Err(res, 'Invalid data; Need "to" and "body" fields.');
  }

  let mailData: DorianMailData = {
    dest: data.to,
    body: data.body
  }

  if(data.subject) {
    mailData.subject = data.subject;
  }

  if(data.from) {
    mailData.from = data.from;
  }
  
  // SEND
  try {
    // TODO we could use functional techniques to make this code way more maintainable...
    //  we need to use composition and Maybe's, perhaps use rambda? Or a fantasy-land
    //  compliant library
    await sendMail(fillDefaults(mailData));
  } catch(err) {
    console.error(err);
    console.error('Mail failure');
    return await send400Err(res, 'Mail failure; sendMail function erroredout:\nMessage: ' + err.message);
  }
  
  // when returning a value, micro sends 200 status
  return 'Successfully sent your mail';
}

export default waitForEmail

package.json

{
  "name": "dorian-mailer",
  "version": "1.0.0",
  "description": "",
  "engines": {
    "node": ">= 8.0.0"
  },
  "main": "dist/index.js",
  "scripts": {
    "start": "micro-dev -p ${MICRO_EMAIL_PORT:-3256}",
    "start:prod": "micro -p ${MICRO_EMAIL_PORT:-3256}",
    "build": "tsc",
    "dev": "run-p -c \"build -- -w\" start"
  },
  "keywords": [],
  "author": "Sean Newell",
  "license": "UNLICENSED",
  "dependencies": {
    "micro": "9.0.0",
    "nodemailer": "4.1.1"
  },
  "devDependencies": {
    "@types/micro": "^7.3.1",
    "@types/nodemailer": "^3.1.3",
    "micro-dev": "^1.2.3",
    "npm-run-all": "^4.1.1",
    "typescript": "^2.5.3"
  }
}