public EurekaEndpointGroupBuilder regions(Iterable<String> regions) {
        this.regions = ImmutableList.copyOf(requireNonNull(regions, "regions"));
        return this;
    }
Sets the specified {@code regions}. {@link EurekaEndpointGroup} will retrieve the registry information
which belongs to the {@code regions}.
eureka/src/main/java/com/linecorp/armeria/client/eureka/EurekaEndpointGroupBuilder.java