Dog.ts

/*************************************************
 *            Contact Dog Owner
 ************************************************/

async contactOwner(dogId: number, msg: string): Promise<void>
{
    try {
        let ownerEmail = await this._getOwnerEmail(dogId)
        let info = await this._sendEmail(ownerEmail, msg)
        console.log(info.message)
    }
    catch(err) {
        console.error(err)
    }

}

// .query() already returns a Promise
private _getOwnerEmail(dogId: number): Promise<string>
{
    let sql = 'SELECT email FROM owners' +
                'JOIN dogs' +
                    'ON owners.owner_id = dogs.owner_id' +
                    'AND dogs.dog_id = $1'

    return db_.query(sql, [dogId])
}

// mailService.send() uses a callback, return custom Promise
private _sendEmail(email: string, msg): Promise<boolean>
{
    return new Promise((resolve, reject) => {
        mailService.send(email, msg, (err, info) => {

            err ? reject(err) : resolve(info)

        })
    })
}