About error message from fail push notification in API response.

hey, I try run release binary **gorush-v1.9.0-darwin-amd64**, a problem has occurred:

I set config.yml [sync: true].
request: /api/push
response: {"counts":1,"logs":[],"success":"ok"}

but, server error log :

> DEBU[2017/08/12 - 23:29:23] worker number is 8, queue number is 8192
> INFO[2017/08/12 - 23:29:25] {"uri":"/api/push","method":"POST","ip":"::1","content_type":"","agent":"python-requests/2.18.3"}
> DEBU[2017/08/12 - 23:29:25] Start push notification for Android
> ERRO[2017/08/12 - 23:29:55] FCM server error: Post https://fcm.googleapis.com/fcm/send: dial tcp 172.217.24.10:443: i/o timeout
> [GIN] 2017/08/12 - 23:29:55 | 200 | 30.002840023s | ::1 | POST /api/push

What surprised me was that error logs from sending fail notifications did not return.