void refresh0() {
            if (resolverClosed) {
                return;
            }

            if (refreshing) {
                return;
            }
            refreshing = true;

            assert address != null;
            final String hostname = address.getHostName();
            // 'sendQueries()' always successfully completes.
            sendQueries(questions, hostname, originalCreationTimeNanos).thenAccept(entry -> {
                if (executor.inEventLoop()) {
                    maybeUpdate(hostname, entry);
                } else {
                    executor.execute(() -> maybeUpdate(hostname, entry));
                }
            });
        }
Closes all the resources allocated and used by this resolver.

<p>Please note that this method does not clear the {@link CacheEntry} because the
{@link #addressResolverCache} is created by {@link RefreshingAddressResolverGroup} and shared across
from all {@link RefreshingAddressResolver}s. {@link CacheEntry} is cleared when
{@link RefreshingAddressResolverGroup#close()} is called.
core/src/main/java/com/linecorp/armeria/client/RefreshingAddressResolver.java