Please answer these questions before submitting your issue. Thanks!

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

1.10

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN="/Users/xxx/Downloads/projects/golang/bin"
GOCACHE="/Users/xxx/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/xxx/Downloads/projects/golang"
GORACE=""
GOROOT="/usr/local/opt/go/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/opt/go/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="/usr/local/Cellar/gcc/7.3.0_1/bin/gcc-7"
CXX="/usr/local/Cellar/gcc/7.3.0_1/bin/g++-7"
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 -fmessage-length=0 -fdebug-prefix-map=/var/folders/w8/y97pxwvj35xcsw9vmh2s3gzr0000gn/T/go-build575805343=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

ran a simple program

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

func main() {
	urls := make([]string, 3)
	urls[0] = "https://www.usa.gov/"
	urls[1] = "https://www.gov.uk/"
	urls[2] = "//www.gouvernement.fr/"

	for _, u := range urls {
		responseTime(u)
	}
}

func responseTime(url string) {
	start := time.Now()

	res, err := http.Get(url)

	if err != nil {
		log.Fatal(err)
	}

	defer res.Body.Close()

	elapsed := time.Since(start).Seconds()

	fmt.Printf("%s took %v seconds \n", url, elapsed)
}

What did you expect to see?

expected output

What did you see instead?

# crypto/x509
In file included from /System/Library/Frameworks/Security.framework/Headers/AuthSession.h:32:0,
                 from /System/Library/Frameworks/Security.framework/Headers/Security.h:43,
                 from /usr/local/Cellar/go/1.10/libexec/src/crypto/x509/root_cgo_darwin.go:17:
/System/Library/Frameworks/Security.framework/Headers/Authorization.h:193:7: error: variably modified 'bytes' at file scope
  char bytes[kAuthorizationExternalFormLength];
       ^~~~~