change icon from object to string

server/server_firebase.go

@@ -151,6 +151,7 @@ func toFirebaseMessage(m *message, auther auth.Auther) (*messaging.Message, erro
 				"title":    m.Title,
 				"message":  m.Message,
 				"encoding": m.Encoding,
+				"icon":     m.Icon,
 			}
 			if len(m.Actions) > 0 {
 				actions, err := json.Marshal(m.Actions)
@@ -166,11 +167,6 @@ func toFirebaseMessage(m *message, auther auth.Auther) (*messaging.Message, erro
 				data["attachment_expires"] = fmt.Sprintf("%d", m.Attachment.Expires)
 				data["attachment_url"] = m.Attachment.URL
 			}
-			if m.Icon != nil {
-				data["icon_url"] = m.Icon.URL
-				data["icon_type"] = m.Icon.Type
-				data["icon_size"] = fmt.Sprintf("%d", m.Icon.Size)
-			}
 			apnsConfig = createAPNSAlertConfig(m, data)
 		} else {
 			// If anonymous read for a topic is not allowed, we cannot send the message along