There are two problems with this library
1.you must change Priority in HttpMessage struct in file gcm.go to int
2.if every things is ok but you get error Error=DeprecatedEndpoint
go to gcm.go again and on const section change httpAddress from this "https://gcm-http.googleapis.com/gcm/send" to "https://fcm.googleapis.com/fcm/send"
There are two problems with this library 1.you must change Priority in HttpMessage struct in file gcm.go to int 2.if every things is ok but you get error Error=DeprecatedEndpoint go to gcm.go again and on const section change httpAddress from this "https://gcm-http.googleapis.com/gcm/send" to "https://fcm.googleapis.com/fcm/send"