Are you sure this built properly? :P
The backslash might generate errors.

I will prefer installing it directly to ETC something like:

PLIST_FILES="@sample etc/cirus-worker.yml.sample"

post-install:
        ${INSTALL_DATA} ${FILESDIR}/cirrus-worker.yml ${STAGEDIR}${DOCSDIR}/cirrus-worker.yml.sample

And removing pkg-message.

yep, pretty sure, give it a try, and will see.
anyway, thanks for catching this

so it would be better to create a pkg-plist and handle the permissions properly.
and also need to adjust the pkg-message after this change.