many server report " NAT discovery feature not supported by this server"

[introspection3]

Your environment.

• Version: github.com/pion/stun v0.6.1
• Browser: include version
• Other Information - stacktraces, related issues, suggestions how to fix, links for us to have context

What did you do?

What did you expect?

What happened?

[introspection3]

"stun.l.google.com:19302", "stun1.l.google.com:19302", "stun2.l.google.com:19302", "stun3.l.google.com:19302", "stun4.l.google.com:19302",