net/http: race in http2Transport [1.15 backport]

[gopherbot]

@answer1991 requested issue #31192 to be considered for backport to the next 1.15 minor release.

Kubernetes team had already announced GOAWAY feature in Kubernetes v1.19 release notes. However, if Kubernetes enable GOAWAY feature, the client will receive unexpected 500 status code errors which I described at #41234, and there is no workaround. I think backport to golang 1.15 is necessary.

@gopherbot please backport, as Kubernetes is affected and there is no workaround.

[answer1991]

We should also backport #42498.

[cagedmantis]

We are taking a little more time to review this before deciding.

[toothrot]

This is a serious issue with no workaround. Approved.