public ClickHouseRequestManager getManager() {
        ClickHouseRequestManager m = managerRef.get();
        if (m == null) {
            m = ClickHouseRequestManager.getInstance();
            if (!managerRef.compareAndSet(null, m)) {
                m = managerRef.get();
            }
        }
        return m;
    }
Gets manager for the request, which defaults to
{@link ClickHouseRequestManager#getInstance()}.

@return non-null request manager
clickhouse-client/src/main/java/com/clickhouse/client/ClickHouseRequest.java