func (r *routes) OnChange(callback func()) {
	r.Lock()
	defer r.Unlock()
	r.onChange = append(r.onChange, callback)
}
func (r *routes) OnChange(callback func()) {
	r.Lock()
	defer r.Unlock()
	r.onChange = append(r.onChange, callback)
}
func ( r * routes ) OnChange ( callback func ( ) ) { r . Lock ( ) defer r . Unlock ( ) r . onChange = append ( r . onChange , callback ) }
// OnChange appends callback to the functions that will be called whenever the
// routes are recalculated.
OnChange appends callback to the functions that will be called whenever the routes are recalculated .