how to synchronize functions with promises in node.js

hi i'm trying to synchronize my functions with convert callback to promise.
i want to add to all posts, post.authorName field via forEach loop and query to user collection.
first i tried with callbacks but this is async and i need to a sync tool.
so i use promise but still my result is like callback.
this is my code:

var mongo = require('mongodb').MongoClient();
var url = "mongodb://localhost:27017/blog";
var ObjectId = require('mongodb').ObjectID;

var listPosts = function(req, res) {
    find('post', {}, 10, {author: 1})
        .then(function(posts) {

            var myPosts = posts;

            const promises = [];

            myPosts.forEach(function(post) {

                console.log("hi i'm forEach" + '\n');
                console.log(post);
                console.log('\n');

                const promise = new Promise(function(resolve, reject){
                    getPostAuthorName(post.authorID)
                        .then(function(postAuthor){
                            post.authorName = postAuthor;
                        })
                        resolve(); 
                });

                console.log("i'm end of forEach and this is result:");
                console.log(post);
                console.log('\n');

                promises.push(promise);
            });

            Promise.all(promises).then(() => {

                console.log('i should print at end' + '\n');

            });
        });
}

var getPostAuthorName = function(authorID) {
    return new Promise(function(resolve, reject){
        findOne('user', {_id: new ObjectId(authorID)})
            .then(function(result){

                console.log("i'm getPostAuthorName" + '\n');

                resolve(result.name);
            })
    })
}

var find = function(collection, cond = {}, limit = 0, sort = {}) {
    return new Promise(function(resolve, reject){
        mongo.connect(url) 
            .then(function(db){
                db.collection(collection)
                    .find(cond).limit(limit).sort(sort).toArray()
                        .then(function(result){
                            resolve(result);
                        })
            })
    });
}

var findOne = function(collection, cond = {}){
    return new Promise(function(resolve, reject){
        mongo.connect(url)
            .then(function(db){
                db.collection(collection).findOne(cond)
                    .then(function(result){

                        console.log("i'm findOne" + '\n');

                        resolve(result);
                    })
            })
    })
}


listPosts();

and at the end i recieve this result:

hi i'm forEach

{ _id: 59888f418c107711043dfcd6,
  title: 'FIRST',
  content: 'this is my FIRST post',
  timeCreated: 2017-08-07T16:03:13.552Z,
  authorID: '5987365e6d1ecc1cd8744ad4' }


i'm end of forEach and this is result:
{ _id: 59888f418c107711043dfcd6,
  title: 'FIRST',
  content: 'this is my FIRST post',
  timeCreated: 2017-08-07T16:03:13.552Z,
  authorID: '5987365e6d1ecc1cd8744ad4' }


hi i'm forEach

{ _id: 598d60d7e2014a5c9830e353,
  title: 'SECOND',
  content: 'this is my SECOND post',
  timeCreated: 2017-08-07T16:03:13.552Z,
  authorID: '5987365e6d1ecc1cd8744ad4' }


i'm end of forEach and this is result:
{ _id: 598d60d7e2014a5c9830e353,
  title: 'SECOND',
  content: 'this is my SECOND post',
  timeCreated: 2017-08-07T16:03:13.552Z,
  authorID: '5987365e6d1ecc1cd8744ad4' }


i should print at end

i'm findOne

i'm getPostAuthorName

i'm findOne

i'm getPostAuthorName

why functions don't run synchronously. what's the solution?