@Nullable
    public static <T extends RequestContext> T getAndSet(RequestContext ctx) {
        requireNonNull(ctx, "ctx");
        return requestContextStorage.push(ctx);
    }
Sets the specified {@link RequestContext} in the {@link RequestContextStorage} and
returns the old {@link RequestContext}.
core/src/main/java/com/linecorp/armeria/internal/common/RequestContextUtil.java