Does apns support broadcast mode push ？

[liangxm]

Please ensure that you are using the latest version of the master branch before filing an issue.

Also make sure to include logs (if applicable) to help reproduce the issue by setting the GODEBUG=http2debug=2 env var.

1. What version of Go are you using? go version
2. What OS and processor architecture are you using? go env
3. What did you do?
4. What did you expect to see?
5. What did you see instead?

[ringsaturn]

No. https://developer.apple.com/forums/thread/700993