assrt | Assert library for Go | Assertion library

With regular expressions, you can use capturing groups to capture individual parts of the search query and make those available in the result. When replacing strings with something else, you can then also use backreferences to refer to the value of those groups.

Capturing groups are created by simply wrapping things with parentheses. You have already used non-capturing groups in your expression, which are basically capturing groups prefixed by ?: which will cause them not to be available.

So in your case, you can simply wrap your r\d+ part with parentheses: