func (mux *ServeMux) HandleRemove(pattern string) {
	if pattern == "" {
		panic("dns: invalid pattern " + pattern)
	}
	mux.m.Lock()
	delete(mux.z, CanonicalName(pattern))
	mux.m.Unlock()
}
HandleRemove deregisters the handler specific for pattern from the ServeMux.
package dns
import (
	"sync"
)
type ServeMux struct {
	z map[string]Handler
	m sync.RWMutex
}
func NewServeMux() *ServeMux {
	return new(ServeMux)
}
var DefaultServeMux = NewServeMux()
func (mux *ServeMux) match(q string, t uint16) Handler {
	mux.m.RLock()
	defer mux.m.RUnlock()
	if mux.z == nil {
		return nil
	}
	q = CanonicalName(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
			}
			handler = h
		}
	}
	if h, ok := mux.z["."]; ok {
		return h
	}
	return handler
}
func (mux *ServeMux) Handle(pattern string, handler Handler) {
	if pattern == "" {
		panic("dns: invalid pattern " + pattern)
	}
	mux.m.Lock()
	if mux.z == nil {
		mux.z = make(map[string]Handler)
	}
	mux.z[CanonicalName(pattern)] = handler
	mux.m.Unlock()
}
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
	mux.Handle(pattern, HandlerFunc(handler))
}