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Stream stuck when used with mongodb and node10

See original GitHub issue

Hello, I really like Highland and I would like to continue to use it but it starts to be a problem with newest version of node.

The following example works just fine with node 8/9 but stays stuck when using node 10+

const MongoClient = require('mongodb').MongoClient;
const hl = require('highland');

const MONGO_URL = 'mongodb://localhost:27017/';

const DB_NAME = 'someDb';
const COLLECTION = 'someCollection';

const run = async () => {
  const mongo = new MongoClient(url);

  await mongo.connect();
  const cursor = mongo.db(DB_NAME)
    .collection(COLLECTION)
    .find()
    .stream();

  return new Promise((resolve, reject) => {
    return hl(cursor)
    .batch(5)
    .flatten()
    .map(x => console.log(x && x._id))
    .stopOnError(reject)
    .done(resolve);
  });
};

run()
  .catch(console.log)
  .then(() => process.exit())

If you replace the mongoDb stream by a simple stream like this one it works just fine:

class Counter extends Readable {
  constructor(opt) {
    super({ ...opt, objectMode: true });
    this._max = 1000000;
    this._index = 1;
  }

  _read() {
    const i = this._index++;
    if (i > this._max)
      this.push(null);
    else {
      this.push({ count: i });
    }
  }
}

Thing is I had a look at the stream implementation inside mongoDB lib and they used the node stream implementation, I have seen nothing weird about it. And something else is a little bit strange, if you remove the flatten inside the hl chain, the stream will not be stucked anymore(even with node10).

Anyway I have no clue what the problem is so if anyone has an idea please share it.