Leaking sessions

[morkai]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
MongoDB sessions created by using mongoose.connection.transaction() aren't cleaned up, resulting in the memory leaking:

If the current behavior is a bug, please provide the steps to reproduce.

const mongoose = require('mongoose');

mongoose.model('Test', new mongoose.Schema({}));

async function main()
{
  await mongoose.connect('mongodb://127.0.0.1:27017/test');
  
  setTimeout(leak, 1000);
}

async function leak()
{
  await mongoose.connection.transaction(async session =>
  {
    await mongoose.model('Test').findOne().session(session).exec();
  });
  
  console.log(
    new Date().toISOString(),
    'sessions =',
    mongoose.connection.client.topology.s.sessions.size
  );
  
  setTimeout(leak, 1000);
}

main();

$ node leak.js
2022-01-23T17:14:16.521Z sessions = 1
2022-01-23T17:14:17.542Z sessions = 2
2022-01-23T17:14:18.555Z sessions = 3
2022-01-23T17:14:19.563Z sessions = 4
2022-01-23T17:14:20.580Z sessions = 5
2022-01-23T17:14:21.603Z sessions = 6
2022-01-23T17:14:22.621Z sessions = 7
2022-01-23T17:14:23.631Z sessions = 8
2022-01-23T17:14:24.645Z sessions = 9
2022-01-23T17:14:25.662Z sessions = 10
...

What is the expected behavior?
mongoose.connection.transaction() should call session.endSession() so the session is cleaned up.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
node v16.13.2
mongoose v6.1.7
mongodb server v5.0.5 driver v4.3.0

[Uzlopak]

Created a PR #11259