This is not a bug. From the documentation for package flag:

Flag parsing stops just before the first non-flag argument ("-" is a non-flag argument) or after the terminator "--".

and your --env flag appears after the terminator "--", so it's correctly not being parsed.

This is a common idiom you will see in many command line tools, not just Go.

-- terminates the argument parser explicitly, because sometimes you have arguments, such as file names, that start with - which you want to capture as a value instead of a flag.

well then you know what i am trying to do. so what is the solution?

Flags in tests are really no different than in any other program, except that you don't get to call flag.Parse() yourself:

package main

import (
	"flag"
	"log"
	"os"
	"testing"
)

var x = flag.Bool("env", false, "")

// run with `go test --env`
func TestFlags(t *testing.T) {
	log.Println(os.Args)     // /tmp/go-build197321626/b001/tmp.lW3vriEIbp.test -test.timeout=10m0s --env
	log.Println(flag.Args()) // []
	log.Println(*x)          // true
}

To treat arguments as flags create a dedicated FlagSet:

// run with `go test -- --env`
func TestArgs(t *testing.T) {
	fs := flag.NewFlagSet("my-test", flag.ContinueOnError)
	y := fs.Bool("env", false, "")

	log.Println(os.Args)     // [/tmp/go-build483180072/b001/tmp.lW3vriEIbp.test -test.timeout=10m0s -- --env]
	log.Println(flag.Args()) // [--env]

	if err := fs.Parse(flag.Args()); err != nil {
		t.Fatal(err)
	}

	log.Println(*y) // true
}

The docs for the interaction between testing and flag.Parse were a bit ambiguous, so I made them clearer a couple of weeks ago in #38952.

If anything is still confusing, please suggest doc improvements. Aside from that, I agree that the current behavior seems to be correct.

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)