How to implement grouping functionality? In net/http, it is implemented like this:

Create two http.ServeMux, one for v1 and one for v2:

func main() {
	mux := http.NewServeMux()
 
	v1 := http.NewServeMux()
	v2 := http.NewServeMux()
 
	mux.Handle("/v1/", http.StripPrefix("/v1", v1))
	mux.Handle("/v2/", http.StripPrefix("/v2", v2))
}

mux.Handle forwards requests starting with /v1/ to v1, and http.StripPrefix simply removes the /v1 prefix from the request URL.

However, this way of grouping is somewhat inconvenient. Let’s optimize it using the previously defined ServeMux struct:

type ServeMux struct {
  http.ServeMux
}

Write a Group method for it, which returns a new *ServeMux:

func (m *ServeMux) Group(pattern string) *ServeMux {
	subMux := &ServeMux{
		ServeMux: http.ServeMux{},
	}
 
	// Remove the trailing "/"
	stripPattern := strings.TrimSuffix(pattern, "/")
	m.ServeMux.Handle(pattern, http.StripPrefix(stripPattern, subMux))
 
	return subMux
}

This is the main logic for grouping. For the complete implementation, please refer to: https://github.com/aeilang/httpz/blob/main/http.go