func (session *Session) Push(data []byte) error {
    if !session.isReady {
        return errors.New("failed to push push: not connected")
    }
    for {
        err := session.UnsafePush(data)
        if err != nil {
            session.logger.Println("Push failed. Retrying...")
            select {
            case <-session.done:
                return errShutdown
            case <-time.After(resendDelay):
            }
            continue
        }
        select {
        case confirm := <-session.notifyConfirm:
            if confirm.Ack {
                session.logger.Println("Push confirmed!")
                return nil
            }
        case <-time.After(resendDelay):
        }
        session.logger.Println("Push didn't confirm. Retrying...")
    }
}