net/http: Re-connect with upgraded HTTP2 connection fails to send Request.body [1.14 backport]

[gopherbot]

@networkimprov requested issue #32441 to be considered for backport to the next 1.14 minor release.

@gopherbot please backport, as Kubernetes is affected.

[andybons]

Approved as this is a serious enough regression with no suitable workaround.

[gopherbot]

Change https://golang.org/cl/242117 mentions this issue: [release-branch.go1.14] net/http: handle body rewind in HTTP/2 connection loss better

[andybons]

This change caused a number of issues when tested internally, and it seems that the fix to #39533 must also be backported if we want to avoid the same fate externally. This backport cannot be landed until the follow-up fix is cherry-picked.

As we are aiming to release the next point release today, I’m pushing this off for now. Apologies for the inconvenience.