Version

• oapi-codegen: v2.8.0
• Go: go1.26.5
• Generator: std-http-server

Minimal reproduction

Configuration:

package: api
output: server.gen.go
generate:
  std-http-server: true

OpenAPI specification:

openapi: 3.0.3
info:
  title: Custom action reproduction
  version: 1.0.0
paths:
  /resources/{resourceId}:apply:
    post:
      operationId: applyResource
      parameters:
        - name: resourceId
          in: path
          required: true
          schema:
            type: string
      responses:
        "204":
          description: Applied

The generated std-http-server registration is equivalent to:

m.HandleFunc(
	http.MethodPost+" "+options.BaseURL+"/resources/{resourceId}:apply",
	wrapper.ApplyResource,
)

Registering that pattern with http.ServeMux panics:

panic: parsing "POST /resources/{resourceId}:apply": at offset 16: bad wildcard segment (must end with '}')

This can also be reproduced without generated code:

mux := http.NewServeMux()
mux.HandleFunc(
	"POST /resources/{resourceId}:apply",
	func(http.ResponseWriter, *http.Request) {},
)

Although Go 1.22+ supports whole-segment wildcards, a mixed wildcard and literal
segment is not valid. Registering /resources/{resourceId} instead accepts the
request, but PathValue("resourceId") returns abc:apply for
/resources/abc:apply; ServeMux does not strip the action suffix.

Expected behavior

For std-http-server, either:

1. generate a compatible route that matches the whole segment, validates and
   strips the literal suffix, and passes abc as resourceId; or
2. reject this path shape during generation with a clear unsupported-route
   error instead of generating code that panics during server startup.

Literal suffixes on templated path segments are useful for custom action routes
such as {resourceId}:apply.

Additional context

The v2.8.0 trailing-slash and handler-registration-order fixes do not cover this
path shape. A local workaround is to register
/resources/{resourceIdAction}, dispatch based on the :apply suffix, and set
the original resourceId path value before invoking the generated wrapper.

The minimal reproduction snippets in this issue may be used under Apache-2.0.