@Nullable
            @Override
            public Endpoint selectNow(ClientRequestContext ctx) {
                // Intentionally return null to simulate that the EndpointGroup become empty when
                // initializing context. for case 2)
                return null;
            }
Reproduce a race case about an endpoint selection that occurs if the following two conditions are met.
1) An EndpointGroup resolved and has non-empty endpoints when creating a ArmeriaClientCall.
2) The endpoints in the EndpointGroup become empty when the ArmeriaClientCall initializing context.
grpc/src/test/java/com/linecorp/armeria/client/grpc/LazyDynamicEndpointGroupTest.java