Error chain in NodeJs with sychronize

I wrote a function to create a user profile.

I use the synchronise module to get rid of the callback hell.

When I do this, everything works fine:

    var sql = jsonSql.build({
        type: 'insert',
        table: 'tbl_user',
        values: {firstname: data.firstname, lastname: data.lastname, email: data.email, website: data.website, password: data.hashedPassword},
    });

    try {
        var query = sync.await(db.query(sql.query, sql.values, sync.defer()));
    } catch (err) {
        res.status(500).send(err);
        return;
    }

When sql finds a user with an already used mail address it sends an error. Perfect.

Then I thought it would be a good idea to separate the code where the user is written into the database, because maybe you want to create a user in the admin-backend and then I could reuse the smaller function.

The smaller function:

function createUserInDB(data) {

    var sql = jsonSql.build({
        type: 'insert',
        table: 'tbl_user',
        values: {firstname: data.firstname, lastname: data.lastname, email: data.email, website: data.website, password: data.hashedPassword},
    });

    return db.query(sql.query, sql.values);
}

Which now gets called from the main function:

try {
        var query = sync.await(userService.createUserInDB(data, sync.defer()));
        console.dir(query);
    } catch(err) {
        console.dir(err);
        res.status(500).send(err);
        return;
    }

This does not work.

How can I get the result of the smaller function (as error or query result) in my main function, so I am able to use try / catch?

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