generalized event handler

app/dns/server/server.go

@@ -52,7 +52,7 @@ func NewCacheServer(ctx context.Context, config *dns.Config) (*CacheServer, erro
 		servers: make([]NameServer, len(config.NameServers)),
 		hosts:   config.GetInternalHosts(),
 	}
-	space.OnInitialize(func() error {
+	space.On(app.SpaceInitializing, func(interface{}) error {
 		disp := dispatcher.FromSpace(space)
 		if disp == nil {
 			return newError("dispatcher is not found in the space")