Data race while using http.Client concurrently

[pmalekn]

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

$ go version
go version go1.12.2 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/pmalek/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/pmalek/.gvm/pkgsets/go1.12.2/global"
GOPROXY=""
GORACE=""
GOROOT="/Users/pmalek/.gvm/gos/go1.12.2"
GOTMPDIR=""
GOTOOLDIR="/Users/pmalek/.gvm/gos/go1.12.2/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/pmalek/code/project/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/zy/lzyp__pd7vx6762s5jcgkkl80000gn/T/go-build893261005=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Use http.Client concurrently

// c.client initialized like so:
// &http.Client{}
var buf bytes.Buffer
// write JSON to buff....
request, err := http.NewRequest("POST", url, &buf)
if err != nil {
	return nil, err
}
request.SetBasicAuth(c.D, c.SessionKey)
request.Header.Add("Content-type", "application/x-ldjson")
rsp, err := c.client.Do(request)

What did you expect to see?

No data race

What did you see instead?

==================
WARNING: DATA RACE
Read at 0x00c001112840 by goroutine 180:
  github.com/org/repo/project/someclient.(*SomeClient).SendStuff()
      /Users/pmalek/.gvm/gos/go1.12.2/src/bytes/buffer.go:68 +0xa63
  github.com/org/repo/otherproject.(*replay).sendSomething.func1()
      /Users/pmalek/code/repo/project/directory/client.go:81 +0x1a52

Previous write at 0x00c001112840 by goroutine 138:
  bytes.(*Buffer).Read()
      /Users/pmalek/.gvm/gos/go1.12.2/src/bytes/buffer.go:101 +0xb5
  io/ioutil.(*nopCloser).Read()
      <autogenerated>:1 +0x87
  net/http.(*http2clientStream).writeRequestBody()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/h2_bundle.go:7664 +0x64d
  net/http.(*http2Transport).getBodyWriterState.func1()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/h2_bundle.go:8878 +0x13d

Goroutine 180 (running) created at:
  github.com/org/repo/otherproject.(*replay).sendSomething()
      /Users/pmalek/code/repo/otherproject/replay.go:187 +0x6a5

Goroutine 138 (running) created at:
  net/http.http2bodyWriterState.scheduleBodyWrite()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/h2_bundle.go:8925 +0x12f
  net/http.(*http2ClientConn).roundTrip()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/h2_bundle.go:7465 +0x90f
  net/http.(*http2Transport).RoundTripOpt()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/h2_bundle.go:6867 +0x23d
  net/http.http2noDialH2RoundTripper.RoundTrip()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/h2_bundle.go:6829 +0x4c
  net/http.(*Transport).roundTrip()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/transport.go:430 +0x14d9
  net/http.(*Transport).RoundTrip()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/roundtrip.go:17 +0x42
  net/http.send()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/client.go:250 +0x6a9
  net/http.(*Client).send()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/client.go:174 +0x1cb
  net/http.(*Client).do()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/client.go:641 +0x4ef
  github.com/org/repo/project/someclient.(*SomeClient).SendStuff()
      /Users/pmalek/.gvm/gos/go1.12.2/src/net/http/client.go:509 +0x4b7
  github.com/org/repo/otherproject.(*replay).sendSomething.func1()
      /Users/pmalek/code/repo/project/directory/client.go:81 +0x1a52
==================

[pmalekn]

It seems that this is connected to (or even a duplicate of) #31192

[bcmills]

Looking at the stack trace, that seems to be the case.

[bcmills]

Duplicate of #31192