You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: serve_mux.go
    path of file: ./repos/goHackTools/vendor/github.com/miekg/dns
    
    the code of the file until where you have to start completion: package dns

import (
	"strings"
	"sync"
)

// ServeMux is an DNS request multiplexer. It matches the zone name of
// each incoming request against a list of registered patterns add calls
// the handler for the pattern that most closely matches the zone name.
//
// ServeMux is DNSSEC aware, meaning that queries for the DS record are
// redirected to the parent zone (if that is also registered), otherwise
// the chil
    
func (mux *ServeMux) match(q string, t uint16) Handler {
	mux.m.RLock()
	defer mux.m.RUnlock()
	if mux.z == nil {
		return nil
	}

	q = strings.ToLower(q)

	var handler Handler
	for off, end := 0, false; !end; off, end = NextLabel(q, off) {
		if h, ok := mux.z[q[off:]]; ok {
			if t != TypeDS {
				return h
			}
			// Continue for DS to see if we have a parent too, if so delegate to the parent
			handler = h
		}
	}

	// Wildcard match, if we have found nothing try the root zone as a last resort.
	if h, ok := mux.z["."]; ok {
		return h
	}

	return handler
}