CACHE [cached directories...]
CACHE instruction makes specific files/directories be shared across runs,
almost always as a performance improvement.
See the tuning performance documentation for more details.
CACHE /var/cache/aptto speed up
RUN apt-get update
CACHE ~/.cache/go-buildto speed up
RUN go install
CACHE ~/.npm ~/.next/cache ~/.yarn/cacheto speed up
Each webapp.io account gets a fixed amount of cache storage, and we periodically delete old or inactive caches.