Mocha and Chai is giving error of not calling done() even after it is called

Question

I have few test cases to test the REST API and everything is in Typescript. I am also using docker to dockerize my application. I have 3 containers which are REST_API_app, MongoDB, api_testing_container. I create the container api_testing_container once other two are created and it uses the same image that is build for REST_API_app. Also I've seen lot of posts about increasing the timeout of mocha using --timeut but that is not what I am looking for and it also does not work in my code, I've tried it. My test case file looks like this :

import { expect } from 'chai';
import request from 'supertest';

import app from '../app';
import * as mongodb from '../mongo/connection';

describe('Testing the API', () => {

    before((done) => {
        mongodb.connectMock()
            .then(() => done())
            .catch((err:any) => done(err))
    })

    it('OK, adding new employee', (done) => {
        request(app).put('/add')
            .send(<some JSON data>)
            .then(res => {
                ...some matcher
                done();
            })
            .catch(err => done(err));
    })

   it('OK, getting all employees', (done) => {
        request(app).get('/all')
            .then(res => {
                ...some matcher
                done();
            })
            .catch(err => { 
                done(err)
            });
    })

   it('OK, getting employee by ID', (done) => {

        request(app)
            .get(`/create/${id}`)
            .then(res => {
                ...some matcher
                done();
            })
            .catch(err => done(err));
    }) 
})

When I try to run the above test cases it perfectly runs on local machine without docker, but when I create all three containers with docker-compose it shows the following error in test container

api_testing_container |   Testing the API
    1) "before all" hook for "OK, adding new employee"b
api_testing_container | 
api_testing_container | 
api_testing_container |   0 passing (20s)
api_testing_container |   1 failing
api_testing_container | 
api_testing_container |   1) Testing the API
api_testing_container |        "before all" hook for "OK, adding new employee":
api_testing_container |      Error: Timeout of 20000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/usr/src/app/src/test/employee.spec.ts)
api_testing_container |       at listOnTimeout (internal/timers.js:549:17)
api_testing_container |       at processTimers (internal/timers.js:492:7)

My mongodb connection for mock looks like this. It seems the error is in this file when I put console.log("test") before mongoose.connect() it does not print it.

import mongoose from 'mongoose';
import {Mockgoose} from 'mockgoose';

export let connect = () => {
  return new Promise((resolve, reject) => {
      const uri: string = 'mongodb://mongo:27017/rest_api_container';
      mongoose.connect( uri, { useNewUrlParser: true, useUnifiedTopology: true })
                .then(() => { 
                  console.log('MongoDB Connected'); 
                  resolve();
                })
                .catch(err => {
                  console.log(err)
                  reject();
                });
  })

}

export let connectMock = () => {
  return new Promise((resolve, reject) => {

    let mockgoose: Mockgoose = new Mockgoose(mongoose);

    mockgoose.prepareStorage()
              .then(() => { 
                const uri: string = 'mongodb://mongo:27017/rest_api_container';
                mongoose.connect( uri, { useNewUrlParser: true, useUnifiedTopology: true })
                          .then((res) => { 
                            console.log('Mock MongoDB Connected'); 
                            resolve(res);
                          })
                          .catch((err :any)=> {
                            console.log(err)
                            reject(err);
                          });
              })
              .catch((err: any) => {
                console.log(err);
                reject(err)
              })
  })
}