writing-asyncawait.md-async-lib.js

const run = (userId) => {
  async.waterfall([
    callback => {
      async.parallel([
        cb => getUser(userId, cb),
        cb => getPosts(userId, cb),
      ], callback);
    },
    ([user, posts], callback) => {
      getComments(posts, (err, comments) => callback(err, user, posts, comments));
    },
    (user, posts, comments, callback) => {
      parsePostsWithComments(user, posts, comments, callback);
    },
  ], (err, postsWithComments) => {
    if (err) {
      console.log('err', err);
    } else
      console.log('postsWithComments', postsWithComments);
  });
}