Hello and thank you for developing this package.

I was trying to use Topic Subscription and Topic Notification, but I'm having some difficulties.

When I try to subscribe a token to a topic, fmt.Printf("Firebase response is: %v", response) returns Firebase response is: &{ [map[]] 200 OK 200}.

When then I try to send a message to that topic, response is {true 200 0 0 0 0 [] NUMERIC_CODE }.

It seems like I have messed up something in the subscription, but I don't know what.

// subscription snippet
package subscription

apiKey := "API_KEY"
topics := []string{"/topics/t1", "/topics/t2"}
tokens := []string{"token1", "token2", "token3"}
client := fcm.NewFcmClient(apiKey)
for _, topic := range topics {
  response, err := client.BatchSubscribeToTopic(tokens, topic)
  if err != nil {
  // log err
  }
}

// sending snippet
package sending

apiKey := "API_KEY"
payload := &fcm.NotificationPayload{
  Title:  "title"
  Body: "body"
}
client = fcm.NewFcmClient(apiKey)
client.SetNotificationPayload(payload)
data := map[string]string{
  "source":   "source",
  "category": "category",
}
topics := []string{"/topics/t1", "/topics/t2"}
for _, topic := range topics {
  client.NewFcmMsgTo(topic, data)
}
status, err := client.Send()
if err != nil {
  // log err
}

If I try to send the same message using NewFcmRegIdsMsg it works

// sending snippet
package sending

apiKey := "API_KEY"
payload := &fcm.NotificationPayload{
  Title:  "title"
  Body: "body"
}
client = fcm.NewFcmClient(apiKey)
client.SetNotificationPayload(payload)
data := map[string]string{
  "source":   "source",
  "category": "category",
}
tokens := []string{"token1", "token2", "token3"}
client.NewFcmRegIdsMsg(tokens, data)
status, err := client.Send()
if err != nil {
  // log err
}

Thank you for your attention

Hi,
quick question is this library thread safe?

Thanks

thank you for the package, I have problems when using this package, when I will send a notification, sometimes it sends sometimes it timeouts, is there a solution?

I will create topic in golang, how to implentation in go-fcm?

Thanks

Have you any example of FCM push notification?

Please add feature - add custom Image into Notification.

https://firebase.google.com/docs/cloud-messaging/android/send-image

There doesn't appear to be a way to send the mutable-content flag iOS needs to be able to modify the notification nation on the fly

Is it possible to use just push notifications?

I am trying to send a simple notification using your library and following you simple example.
I get Invalid Registration. I have tried many different keys from Firebase Project settings as written. But the result is always the same:
Key: AAAAVC5OXEc:APA91bE_-H82q9b4qo1Bh9COR5w3VrLz4FjTN19y-TgXsY2JVEPs2_mtJQr_xOaDFCVC-nhoaMHXV7bklcG8DVkhUFbUNaMK9-FMrii3lBwzKrLsGmlrCGtF5BSC2pVKCRLvAvm5jgxo

Status Code   : 200
Success       : 0
Fail          : 1
Canonical_ids : 0
Topic MsgId   : 0
Topic Err     : 
Result(0)> 
         error  :  InvalidRegistration

Probably it should return this, just like all other methods. I can make PR if needed.

See the migration instructions here: https://firebase.google.com/docs/cloud-messaging/migrate-v1

HTTP requests before:

POST https://fcm.googleapis.com/fcm/send
After:

POST https://fcm.googleapis.com/v1/projects/myproject-b5ae1/messages:send

DefaultEndpoint = "https://fcm.googleapis.com/fcm/send"
Are there plans to update this Endpoint in the library?

I'm trying to use your library with the sample application of posting to a topic. Every time I send a request I get a PROTOCOL_ERROR message back. Here's what I'm doing in Go

fcmClient := fcm.NewFcmClient(ApiKey)
    go func() {
        for {
            // Add ourselves into the worker queue.
            w.WorkerQueue <- w.Work

            select {
            case work := <-w.Work:
                //arr := []byte(work.Message)

                log.Println(work.Message)
                data := map[string]string{
                    "msg": work.Message,
                }
                topic := "/topics/" + work.Topic
                log.Println("Topic:", topic)
                fcmClient.NewFcmMsgTo(topic, data)
                status, err := fcmClient.Send()
                if err == nil {
                    status.PrintResults()
                } else {
                    status.PrintResults()
                    log.Println(err)
                }
                // Receive a work request.
                //log.Println("Job Received")
                //fmt.Printf("worker%d: Hello, %s!\n", w.ID, work.Name)

            case <-w.QuitChan:
                // We have been asked to stop.
                fmt.Printf("worker%d stopping\n", w.ID)
                return
            }
        }
    }()

This is what I get back:

2016/09/20 16:53:27 Post https://fcm.googleapis.com/fcm/send: stream error: stream ID 1; PROTOCOL_ERROR

I've tested my keys using curl and hand crafting the JSON to send to FCM and everything is coming back successful.

Hello there 👋

First of all thanks for the work you've put in this library 🎉

I just noticed that on the Firebase project's setting page :

Firebase Cloud Messaging tokens have replaced server keys for sending messages. While you may continue to use them, support is being deprecated for server keys.

Would that be possible for you to add support for the FCM Tokens ?

Thanks a lot 🙇

Would you please provide an example of sending an image in the notification message?