diff --git a/notify/feedback.go b/notify/feedback.go
index 790404c..c4f873e 100644
--- a/notify/feedback.go
+++ b/notify/feedback.go
@@ -13,7 +13,7 @@ import (
 // DispatchFeedback sends a feedback to the configured gateway.
 func DispatchFeedback(log logx.LogPushEntry, url string, timeout int64) error {
 	if url == "" {
-		return errors.New("The url can't be empty")
+		return errors.New("url can't be empty")
 	}
 
 	payload, err := json.Marshal(log)
diff --git a/notify/notification.go b/notify/notification.go
index d2f82c7..2233094 100644
--- a/notify/notification.go
+++ b/notify/notification.go
@@ -197,12 +197,12 @@ func SetProxy(proxy string) error {
 // CheckPushConf provide check your yml config.
 func CheckPushConf(cfg *config.ConfYaml) error {
 	if !cfg.Ios.Enabled && !cfg.Android.Enabled && !cfg.Huawei.Enabled {
-		return errors.New("Please enable iOS, Android or Huawei config in yml config")
+		return errors.New("please enable iOS, Android or Huawei config in yml config")
 	}
 
 	if cfg.Ios.Enabled {
 		if cfg.Ios.KeyPath == "" && cfg.Ios.KeyBase64 == "" {
-			return errors.New("Missing iOS certificate key")
+			return errors.New("missing iOS certificate key")
 		}
 
 		// check certificate file exist
diff --git a/notify/notification_apns.go b/notify/notification_apns.go
index 5b6c5d3..d1b2a9d 100644
--- a/notify/notification_apns.go
+++ b/notify/notification_apns.go
@@ -286,8 +286,8 @@ func iosAlertDictionary(payload *payload.Payload, req *PushNotification) *payloa
 }
 
 // GetIOSNotification use for define iOS notification.
-// The iOS Notification Payload
-// ref: https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/PayloadKeyReference.html#//apple_ref/doc/uid/TP40008194-CH17-SW1
+// The iOS Notification Payload (Payload Key Reference)
+// Ref: https://apple.co/2VtH6Iu
 func GetIOSNotification(req *PushNotification) *apns2.Notification {
 	notification := &apns2.Notification{
 		ApnsID:     req.ApnsID,
@@ -372,17 +372,19 @@ func GetIOSNotification(req *PushNotification) *apns2.Notification {
 }
 
 func getApnsClient(cfg *config.ConfYaml, req *PushNotification) (client *apns2.Client) {
-	if req.Production {
+	switch {
+	case req.Production:
 		client = ApnsClient.Production()
-	} else if req.Development {
+	case req.Development:
 		client = ApnsClient.Development()
-	} else {
+	default:
 		if cfg.Ios.Production {
 			client = ApnsClient.Production()
 		} else {
 			client = ApnsClient.Development()
 		}
 	}
+
 	return
 }
 
@@ -430,7 +432,7 @@ Retry:
 
 				status.StatStorage.AddIosError(1)
 				// We should retry only "retryable" statuses. More info about response:
-				// https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/handling_notification_responses_from_apns
+				// See https://apple.co/3AdNane (Handling Notification Responses from APNs)
 				if res != nil && res.StatusCode >= http.StatusInternalServerError {
 					newTokens = append(newTokens, token)
 				}
diff --git a/notify/notification_apns_test.go b/notify/notification_apns_test.go
index a69a587..2c76e11 100644
--- a/notify/notification_apns_test.go
+++ b/notify/notification_apns_test.go
@@ -30,7 +30,7 @@ func TestDisabledAndroidIosConf(t *testing.T) {
 	err := CheckPushConf(cfg)
 
 	assert.Error(t, err)
-	assert.Equal(t, "Please enable iOS, Android or Huawei config in yml config", err.Error())
+	assert.Equal(t, "please enable iOS, Android or Huawei config in yml config", err.Error())
 }
 
 func TestMissingIOSCertificate(t *testing.T) {
@@ -42,7 +42,7 @@ func TestMissingIOSCertificate(t *testing.T) {
 	err := CheckPushConf(cfg)
 
 	assert.Error(t, err)
-	assert.Equal(t, "Missing iOS certificate key", err.Error())
+	assert.Equal(t, "missing iOS certificate key", err.Error())
 
 	cfg.Ios.KeyPath = "test.pem"
 	err = CheckPushConf(cfg)