diff --git a/next/assets/assets.go b/next/assets/assets.go
index 04e855c..0b5eee2 100644
--- a/next/assets/assets.go
+++ b/next/assets/assets.go
@@ -2,6 +2,7 @@ package assets
 
 import (
 	"XProxy/next/logger"
+	"github.com/robfig/cron"
 	urlpkg "net/url"
 	"strings"
 	"sync"
@@ -12,63 +13,109 @@ var buildinAssets = map[string]string{
 	"geosite.dat": "/geosite.dat.xz",
 }
 
-type UpdateSettings struct {
-	cron   string
-	mutex  sync.Mutex
-	proxy  *urlpkg.URL
-	assets map[string]string
+type updateConfig struct {
+	spec    string
+	cron    *cron.Cron
+	renew   sync.Mutex
+	running sync.Mutex
+	proxy   *urlpkg.URL
+	assets  map[string]string
 }
 
-var update UpdateSettings
+var update updateConfig
 
-func assetsClone(raw map[string]string) map[string]string {
-	assets := make(map[string]string, len(raw))
-	for file, url := range raw {
-		assets[file] = strings.Clone(url)
-	}
-	return assets
-}
+//func assetsClone(raw map[string]string) map[string]string {
+//	assets := make(map[string]string, len(raw))
+//	for file, url := range raw {
+//		assets[file] = strings.Clone(url)
+//	}
+//	return assets
+//}
 
-func SetCron(cron string) error {
-	// TODO: setting up crond service
-	return nil
+// GetCron is used to obtain cron service specification.
+func GetCron() string {
+	update.renew.Lock()
+	spec := strings.Clone(update.spec)
+	update.renew.Unlock()
+	return spec
 }
 
-func GetProxy() string {
-	update.mutex.Lock()
-	proxy := update.proxy.String()
-	update.mutex.Unlock()
-	return proxy
-}
+// SetCron is used to update cron service specification.
+func SetCron(spec string) error {
+	if spec == update.spec {
+		return nil // cron spec without renew
+	}
 
-func SetProxy(proxy string) error {
-	var proxyUrl *urlpkg.URL // clear proxy by empty string
-	if proxy != "" {
-		url, err := urlpkg.Parse(proxy)
+	var cs *cron.Cron
+	if spec != "" { // update cron service
+		cs = cron.New()
+		err := cs.AddFunc(spec, func() {
+			var entry *cron.Entry
+			if entries := update.cron.Entries(); len(entries) != 0 && entries[0] != nil {
+				entry = entries[0]
+			}
+			logger.Debugf("hello from cron")
+			if entry != nil {
+				logger.Debugf("Assets cron service next trigger -> `%s`", entry.Next)
+			}
+		})
 		if err != nil {
-			logger.Errorf("Invalid proxy url `%s` -> %v", proxy, err)
+			logger.Errorf("Invalid cron spec `%s` -> %v", spec, err)
 			return err
 		}
-		proxyUrl = url
+		cs.Start()
 	}
-	update.mutex.Lock()
-	update.proxy = proxyUrl
-	update.mutex.Unlock()
-	return nil
-}
 
-func SetAssets(assets map[string]string) {
-	update.mutex.Lock()
-	update.assets = assetsClone(assets)
-	update.mutex.Unlock()
+	update.renew.Lock()
+	if update.cron != nil {
+		update.cron.Stop() // stop old cron service
+	}
+	update.cron = cs
+	update.spec = spec
+	if cs == nil {
+		logger.Infof("Assets cron service has been terminated")
+	} else {
+		logger.Infof("Assets cron service has been updated -> `%s`", spec)
+	}
+	update.renew.Unlock()
+	return nil
 }
 
-func GetAssets() map[string]string {
-	update.mutex.Lock()
-	assets := assetsClone(update.assets)
-	update.mutex.Unlock()
-	return assets
-}
+//func GetProxy() string {
+//	update.mutex.Lock()
+//	proxy := update.proxy.String()
+//	update.mutex.Unlock()
+//	return proxy
+//}
+//
+//func SetProxy(proxy string) error {
+//	var proxyUrl *urlpkg.URL // clear proxy by empty string
+//	if proxy != "" {
+//		url, err := urlpkg.Parse(proxy)
+//		if err != nil {
+//			logger.Errorf("Invalid proxy url `%s` -> %v", proxy, err)
+//			return err
+//		}
+//		proxyUrl = url
+//	}
+//	update.mutex.Lock()
+//	update.proxy = proxyUrl
+//	update.mutex.Unlock()
+//	return nil
+//}
+//
+//func SetAssets(assets map[string]string) {
+//	update.mutex.Lock()
+//	update.assets = assetsClone(assets)
+//	update.mutex.Unlock()
+//}
+//
+//func GetAssets() map[string]string {
+//	update.mutex.Lock()
+//	assets := assetsClone(update.assets)
+//	update.mutex.Unlock()
+//	return assets
+//}
 
 func LoadBuildin() {
 	updateLocalAssets(buildinAssets, true)
diff --git a/next/assets/update.go b/next/assets/update.go
index ddec46f..b09aa64 100644
--- a/next/assets/update.go
+++ b/next/assets/update.go
@@ -4,6 +4,7 @@ import (
 	"XProxy/next/logger"
 	urlpkg "net/url"
 	"os"
+	"path"
 	"sync"
 	"time"
 )
@@ -11,14 +12,18 @@ import (
 // saveAsset is used to write to a local file and specify its last modify
 // time. If the file exists, it will be replaced.
 func saveAsset(file string, content []byte, date *time.Time) error {
-	// TODO: create folder if not exist
+	err := os.MkdirAll(path.Dir(file), 0755)
+	if err != nil {
+		logger.Errorf("Failed to create folder -> %v", err)
+		return err
+	}
+
 	fp, err := os.OpenFile(file, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
 	if err != nil {
-		logger.Errorf("Failed to open file `%s` -> %v", file, err)
+		logger.Errorf("Failed to open file -> %v", err)
 		return err
 	}
 	defer fp.Close()
-
 	_, err = fp.Write(content)
 	if err != nil {
 		logger.Errorf("Failed to save file `%s` -> %v", file, err)
diff --git a/next/main.go b/next/main.go
index b9d01c3..2d53645 100644
--- a/next/main.go
+++ b/next/main.go
@@ -1,10 +1,27 @@
 package main
 
-import "XProxy/next/assets"
+import (
+	"XProxy/next/assets"
+	"XProxy/next/logger"
+	"time"
+)
 
 func main() {
 
-	assets.LoadBuildin()
+	logger.Warnf("cron -> `%s`", assets.GetCron())
+	assets.SetCron("@every 1s")
+	logger.Warnf("cron -> `%s`", assets.GetCron())
+
+	time.Sleep(5 * time.Second)
+	assets.SetCron("@every 2s")
+	logger.Warnf("cron -> `%s`", assets.GetCron())
+
+	time.Sleep(8 * time.Second)
+	assets.SetCron("")
+	logger.Warnf("cron -> `%s`", assets.GetCron())
+	select {}
+
+	//assets.LoadBuildin()
 
 	//remoteAssets := map[string]string{
 	//	"geoip.dat":   "https://cdn.dnomd343.top/v2ray-rules-dat/geoip.dat.xz",