AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE=''
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/smira/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/smira/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2541632811=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/home/smira/Documents/x25519-test/go.mod'
GOMODCACHE='/home/smira/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/smira/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/smira/sdk/go1.25.0'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/smira/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/smira/sdk/go1.25.0/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.25.0'
GOWORK=''
PKG_CONFIG='pkg-config'

package main
import (
	"crypto/fips140"
	"log"
	"net/http"
)
func main() {
	log.Printf("FIPS mode: %v", fips140.Enabled())
	_, err := http.Get("https://golang.org/")
	if err != nil {
		log.Fatalf("http error: %s", err)
	}
}

$ go run main.go
2025年08月27日 15:41:22 FIPS mode: false

$ GODEBUG=fips140=only ~/go/bin/go1.24.0 run main.go
2025年08月27日 16:19:21 FIPS mode: true
2025年08月27日 16:19:21 http error: Get "https://golang.org/": crypto/ecdh: use of X25519 is not allowed in FIPS 140-only mode
exit status 1