Help with new regex Middleware

I do not know go regexes, I am using something like HostRegexp(`{subdomain:[a-z0-9-]+}.domain.tld
and this works in v2.X, but I'm not sure the go version may have some quirky behaviors...
Should I change something or this regex is the same with both the old engine and the new go engine for regexes?


v2.11 doc has a lot of curly brackets.
v3.0 doc has not a single curly bracket.

I missed the 3.0 docs, thank you!
another linked questions: if I pass an environment variable like ${DOMAIN} (with it being domain.tld), how should I escape the dot in the middle of the domain?
I would use a regex like ^.+\.${DOMAIN}$
probably I can ignore it honestly because the dot matches everything including the dot,but maybe there is a better way?
well anyway I tested it and now I have the warning "no domain found in rule HostRegexp..."

When using in labels, I know from the auth middleware that at least "special character" $ needs to be escaped. Try to use $$ within ${} content.