auto hb_interval = seconds(workers_.size());
for (auto& worker : workers_) {
    SharedPtr<high_resolution_timer> hb_timer = std::make_shared<high_resolution_timer>(worker->GetIO(), hb_interval);
    SharedPtr<std::function<void(const boost::system::error_code&)> > cb = std::make_shared<std::function<void(const boost::system::error_code&)> >();

    *cb = [this, hb_timer, cb, hb_interval] (const boost::system::error_code& ec) {
        if (ec) {
            return;
        }

        hb_timer->expires_after(hb_interval);
        hb_timer->async_wait(*cb);

        ++hb_;
    };

    hb_timer->async_wait(*cb);
    hb_timers_.push_back(hb_timer);
}