x/net/http2: delayed test failure in TestTransportPingWhenReading

[bcmills]

panic: Fail in goroutine after TestTransportPingWhenReading/two_pings_in_each_serverResponseInterval has completed

goroutine 14781 [running]:
testing.(*common).Fail(0xba2bb5e0)
	/workdir/go/src/testing/testing.go:680 +0x105
testing.(*common).Error(0xba2bb5e0, 0xb8bbcfcc, 0x1, 0x1)
	/workdir/go/src/testing/testing.go:780 +0x62
golang.org/x/net/http2.testTransportPingWhenReading.func2.1(0xb8c80498, 0xb894a5a0, 0xb8922da0, 0xba2bb5e0, 0x3b9aca00, 0x0)
	/workdir/gopath/src/golang.org/x/net/http2/transport_test.go:3514 +0x30b
created by golang.org/x/net/http2.testTransportPingWhenReading.func2
	/workdir/gopath/src/golang.org/x/net/http2/transport_test.go:3500 +0x33d
exitcode=2FAIL	golang.org/x/net/http2	26.736s

2020-09-04T19:48:48-62affa3/android-386-emu
2020-09-04T19:48:48-62affa3/linux-ppc64le-buildlet
2020-08-22T12:43:28-c890458/dragonfly-amd64-5_8
2020-08-22T12:43:28-c890458/freebsd-arm-paulzhol
2020-08-22T12:43:28-c890458/freebsd-arm64-dmgk
2020-08-22T12:43:28-c890458/linux-arm
2020-08-22T12:43:28-c890458/linux-ppc64le-buildlet
2020-08-13T13:45:08-3edf25e/darwin-amd64-10_12
2020-08-13T13:45:08-3edf25e/darwin-amd64-nocgo
2020-08-13T13:45:08-3edf25e/freebsd-arm64-dmgk
2020-08-13T13:45:08-3edf25e/linux-ppc64-buildlet
2020-08-13T13:45:08-3edf25e/linux-ppc64le-buildlet
2020-07-07T03:43:11-ab34263/freebsd-arm64-dmgk
2020-06-25T00:16:55-4c52546/linux-ppc64-buildlet
2020-06-25T00:16:55-4c52546/linux-s390x-ibm
2020-06-25T00:16:55-4c52546/plan9-386-0intro
2020-06-25T00:16:55-4c52546/plan9-amd64-9front
2020-06-02T11:40:24-627f964/dragonfly-amd64
2020-06-02T11:40:24-627f964/freebsd-arm64-dmgk
2020-06-02T11:40:24-627f964/linux-mips-rtrk
2020-06-02T11:40:24-627f964/linux-s390x-ibm
2020-06-02T11:40:24-627f964/plan9-386-0intro
2020-06-02T11:40:24-627f964/plan9-amd64-9front
2020-06-02T11:40:24-627f964/solaris-amd64-oraclerel
2020-05-28T22:51:25-3c3fba1/freebsd-arm64-dmgk
2020-05-28T22:51:25-3c3fba1/linux-ppc64le-buildlet
2020-05-20T18:23:14-0ba52f6/android-386-emu
2020-05-20T18:23:14-0ba52f6/darwin-amd64-10_12
2020-05-20T18:23:14-0ba52f6/darwin-amd64-10_15
2020-05-20T18:23:14-0ba52f6/freebsd-arm64-dmgk
2020-05-20T18:23:14-0ba52f6/linux-ppc64-buildlet
2020-05-20T18:23:14-0ba52f6/linux-ppc64le-buildlet
2020-05-20T18:23:14-0ba52f6/plan9-386-0intro

It looks like the test server starts a goroutine but does not wait for it to complete before the server function exits.

CC @caesarxuchao @bradfitz @fraenkel @neild

[gopherbot]

Change https://golang.org/cl/254278 mentions this issue: net/http2: wait for test goroutines to complete