No, it's just that the Go team have decided to continue with their current contribution process rather than using pull requests. I don't know whether this is a permanent decision or not.
"The Go team will not be accepting pull-requests here. Contributions must still go through the normal code-review process and gerrit. The updated contribution steps are not yet available though."
This is something very similar to that is being planned for FreeBSD repositories on GitHub: automated process turning pull requests into FreeBSD's Bugzilla bug reports and a comment closing the pull request, informing user about the Bugzilla bug link and how to proceed.
Actually that's even better than disabling pull requests entirely. I guess the closing comment will also contain a link to contribution guidelines and such.
Edit: @rurounijones points out that if there's a CONTRIBUTING.md in the repo then Github will show it when someone creates a PR. That's a great feature!
"The Go team will not be accepting pull-requests here. Contributions must still go through the normal code-review process and gerrit. The updated contribution steps are not yet available though."
https://github.com/golang/go/pull/9219