x/net/http2: TestTransportPingWhenReading fails on Plan 9

[millerresearch]

What version of Go are you using (go version)?

Current master on sub-repo builders.

What operating system and processor architecture are you using (go env)?

Plan 9, affects arm, 386 and amd64.

I think this is a new test, introduced in CL198040

Example logs for each GOARCH:
https://build.golang.org/log/aa9acd550974f473c6fa49e100c751e2d64be3d0
https://build.golang.org/log/ab04d68c8dc68e4192029ce39c1429906413efed
https://build.golang.org/log/8b4eb0a7cda60a1af29c2d2b03396aa51aaa2187

[millerresearch]

The new test was using (*TCPConn).CloseWrite which doesn't work on Plan 9, because the Plan 9 kernel's tcp/ip implementation doesn't support half-close. See #17906. I'll send a CL with the usual workaround (call (*TCPConn).Close as well).

[gopherbot]

Change https://golang.org/cl/235217 mentions this issue: x/net/http2: don't rely on TCP CloseWrite in tests on Plan 9