public SELF eventLoop(EventLoop eventLoop) {
        requireNonNull(eventLoop, "eventLoop");
        checkArgument(TransportType.isSupported(eventLoop), "unsupported event loop type: %s", eventLoop);

        this.eventLoop = eventLoop;
        return self();
    }
Sets the {@link EventLoop} to use for sending DNS queries.
core/src/main/java/com/linecorp/armeria/client/endpoint/dns/DnsEndpointGroupBuilder.java