@UnstableApi
    @SuppressWarnings("unchecked")
    public Supplier<AutoCloseable> contextHook() {
        return (Supplier<AutoCloseable>) get(CONTEXT_HOOK);
    }
Returns the {@link Supplier} which provides an {@link AutoCloseable} and will be called whenever this
{@link RequestContext} is popped from the {@link RequestContextStorage}.
core/src/main/java/com/linecorp/armeria/client/ClientOptions.java