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

go version go1.10.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/motomuohtski/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/motomuohtski/go"
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
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"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/3t/1rcsh7wn6sb3_w2nbbnp0zc80000gn/T/go-build234195255=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

1. Have a file ${GOPATH}/src/github.com/motomux/hellobop/src/hellobop.go

package hellobop

import "fmt"

func Hello(name string) string {
        return fmt.Sprintf("Hello %s from binary-only package!", name)
}

2. Have a header file ${GOPATH}/src/github.com/motomux/hellobop/hellobop_header.go

//go:binary-only-package

package hellobop

func Hello(name string) string {
}

3. Build binary by go build -o ${GOPATH}/pkg/darwin_amd64/github.com/motomux/hellobop.a -x ./src

4. Have a test file ${GOPATH}/src/github.com/motomux/hellobop/test/helloboa_test.go

5. Run test by go test ./test

6. Run test by go test -race ./test

Here is the repository to reproduce the issue.

What did you expect to see?

go test -race runs test without any error.

What did you see instead?

It's failed with the error
go build github.com/motomux/hello: missing or invalid binary-only package