public SelectorDTO getSelector(final String id) {
        return getResource("/selector", id, SelectorDTO.class);
    }
Fetch Selector by given id.

@param id of selector that needs to fetch
@return {@link SelectorDTO}
shenyu-e2e/shenyu-e2e-client/src/main/java/org/apache/shenyu/e2e/client/admin/AdminClient.java