cmd/go clean -testcache does not clean test cache

[tendervittles]

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

$ go version
go version go1.12beta2 linux/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
GOARCH="amd64"

GOBIN=""

GOCACHE="/home/tendervittles/.cache/go-build"

GOEXE=""

GOFLAGS=""

GOHOSTARCH="amd64"

GOHOSTOS="linux"

GOOS="linux"

GOPATH="/home/tendervittles/go"

GOPROXY=""

GORACE=""

GOROOT="/usr/local/other/go"

GOTMPDIR=""

GOTOOLDIR="/usr/local/other/go/pkg/tool/linux_amd64"

GCCGO="gccgo"

CC="gcc"

CXX="g++"

CGO_ENABLED="1"

GOMOD=""

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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build703925793=/tmp/go-build -gno-record-gcc-switches"

The only slightly non-standard env is GOROOT="/usr/local/other/go". I use this when testing betas and release candidates.

What did you do?

I created a silly test, ran it twice, and saw the result was cached. Then I cleaned the test cache and ran a third time. The test result was still cached.

package silly

import (
	"testing"
	"time"
)

func TestSilly(t *testing.T) {
	time.Sleep(5 * time.Second)
}

$ go test silly_test.go
ok  	command-line-arguments	5.003s
$ go test silly_test.go
ok  	command-line-arguments	(cached)
$ go clean -testcache
$ go test silly_test.go
ok  	command-line-arguments	(cached)
$

However, clearing the entire cache does force a test run.

$ go clean -cache
$ go test silly_test.go
ok  	command-line-arguments	5.003s
$

What did you expect to see?

A test that took 5 seconds to run.

What did you see instead?

A cached test result.

[gopherbot]

Change https://golang.org/cl/158117 mentions this issue: cmd/go/internal/clean: fix clean -testcache does not clean test cache