Need help on enableEtagSupport - etag not showing

[krisadatreg]

I got the issue when setting enableEtagSupport to be true but no etag included in the response header
What else do I need to do

below are my settings

cache: { enabled: true, type: 'mem', enableEtagSupport: true, enableXCacheHeaders: true, maxAge: CACHE_AGE_MEDIUM, models: [...], ...}