@Override
    protected final void doCloseAsync(CompletableFuture<?> future) {
        final ScheduledFuture<?> scheduledFuture = this.scheduledFuture;
        if (scheduledFuture != null) {
            scheduledFuture.cancel(true);
        }
        future.complete(null);
    }
Stops polling DNS servers for service updates.
core/src/main/java/com/linecorp/armeria/client/endpoint/dns/DnsEndpointGroup.java