[BUG] contrib/dimfeld/httptreemux.v5: default resource namer incorrectly replaces path variables

[devillecodes]

Version of dd-trace-go

v1.65.1

Describe what happened:

The default resource name in the contrib/dimfeld/httptreemux.v5 package has a bug where the path variable replacement fails under certain conditions.

E.g. if you have a route /foo/2by4/bar/:n and request path /foo/2by4/2 then the code will attempt to replace the first occurrence of /2 with /:n which will result in the path: /foo/:nby4/2.

Describe what you expected:

The code should replace the correct variable and leave the rest of the path unaltered.

Steps to reproduce the issue:

1. Include the router in a project.
2. Register a handler for an endpoint, eg. GET /foo/2by4/bar/:n
3. Call the endpoint with the following: GET /foo/2by4/2

Additional environment details (Version of Go, Operating System, etc.):

[darccio]

Thanks for reaching out. We'll review this and fix the issue.