Latest release 2.8.1 does not support define headers for active healthchecks: kong/upstreams.lua at 2.8.1 · Kong/kong · GitHub
But this is already available in master: kong/upstreams.lua at master · Kong/kong · GitHub
Any idea when this will be released?
Kong Gateway 3.0 is around the corner, so this will be available in the next weeks.
It was not included in 2.8.1 because, as a new feature, it is released only in minor or major versions. Patch releases include only fixes for existent features.