net/http, testing: Too many goroutines running after net/http test(s) with -run=Detect

[odeke-em]

Please answer these questions before submitting your issue. Thanks!

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

go version devel +952ecbe Wed Jun 14 21:44:01 2017 +0000 darwin/amd64

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

GOARCH="amd64"
GOBIN="/Users/emmanuelodeke/go/bin"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/emmanuelodeke/go"
GORACE=""
GOROOT="/Users/emmanuelodeke/go/src/go.googlesource.com/go"
GOTOOLDIR="/Users/emmanuelodeke/go/src/go.googlesource.com/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/v3/7z434qpx5v3bw0wh8h2myfpw0000gn/T/go-build090089524=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

While writing the code and tests implementing #20808, I ran

$ go test -v -run=Detect

What did you expect to see?

=== RUN   TestHTTPSClientDetectsHTTPServer
--- PASS: TestHTTPSClientDetectsHTTPServer (0.00s)
=== RUN   TestDetectContentType
--- PASS: TestDetectContentType (0.00s)
PASS

What did you see instead?

=== RUN   TestHTTPSClientDetectsHTTPServer
--- PASS: TestHTTPSClientDetectsHTTPServer (0.00s)
=== RUN   TestDetectContentType
--- PASS: TestDetectContentType (0.00s)
PASS
Too many goroutines running after net/http test(s).
1 instances of:
os/signal.signal_recv(0x0)
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/runtime/sigqueue.go:116 +0xa7
os/signal.loop()
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/os/signal/signal_unix.go:22 +0x22
created by os/signal.init.0
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/os/signal/signal_unix.go:28 +0x41
1 instances of:
testing.(*M).before.func1(0xc420070180)
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1111 +0x38
created by testing.(*M).before
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1110 +0x191
exit status 1
FAIL	net/http	0.540s

I haven't performed a git bissection or an investigation but one can easily check that this problem doesn't exist on Go1.8 but it does on Go1.9Beta1, Go1.9Beta2

[bradfitz]

Weird. I thought I already marked that goroutine as a non-net/http goroutine in a9fc249

[bradfitz]

Oh, you're 18 commits before that.

Sync to head and it should go away. Reopen if not.

[odeke-em]

Still exists on latest tip 81ed9ca. Before filling the bug report, I had just git reverted a bunch of commits trying to quickly find out what had tripped out

$ go version
go version devel +81ed9ca Tue Jun 27 19:00:52 2017 +0000 darwin/amd64
 go test -v -run=Detect
=== RUN   TestHTTPSClientDetectsHTTPServer
--- PASS: TestHTTPSClientDetectsHTTPServer (0.00s)
=== RUN   TestDetectContentType
--- PASS: TestDetectContentType (0.00s)
PASS
Too many goroutines running after net/http test(s).
1 instances of:
testing.(*M).before.func1(0xc420064180)
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1111 +0x38
created by testing.(*M).before
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1110 +0x191
exit status 1
FAIL	net/http	0.540s

[gopherbot]

CL https://golang.org/cl/46836 mentions this issue.