env := os.Getenv("CGO_ENABLED")
	if env == "" {
		env = defaultCGO_ENABLED
	}
	switch env {
	case "1":
		c.CgoEnabled = true
	case "0":
		c.CgoEnabled = false
	default:
		// cgo must be explicitly enabled for cross compilation builds
		if runtime.GOARCH == c.GOARCH && runtime.GOOS == c.GOOS {
			c.CgoEnabled = platform.CgoSupported(c.GOOS, c.GOARCH)
			break
		}

// buildableFiles returns the list of files in the given directory
// that are actually used for the build, given GOOS/GOARCH restrictions.
func buildableFiles(t *testing.T, dir string) []string {
	ctxt := build.Default
	ctxt.CgoEnabled = true
	pkg, err := ctxt.ImportDir(dir, 0)
	if err != nil {
		t.Fatalf("can't find buildable files: %v", err)
	}
	return pkg.GoFiles

	fset      *token.FileSet // positions are relative to fset
	ctx       build.Context
	failed    bool
	donePaths map[string]interface{}
}

func newAnalyzer() *analyzer {
	ctx := build.Default
	ctx.CgoEnabled = true

	a := &analyzer{
		fset:      token.NewFileSet(),
		ctx:       ctx,
		donePaths: make(map[string]interface{}),
	}

	return a
}

// collect extracts test metadata from a file.

		GOARCH       string
		GOEXPERIMENT string
		GODEBUG      string
		CGO_ENABLED  string
	}
	if err := json.NewDecoder(stdout).Decode(&env); err != nil {
		t.Fatal("Decode:", err)
	}
	if err := cmd.Wait(); err != nil {
		t.Fatal("Wait:", err)
	}
	goos = env.GOOS
	goarch = env.GOARCH
	cgoEnabled, _ = strconv.ParseBool(env.CGO_ENABLED)
	goExperiment = env.GOEXPERIMENT
	goDebug = env.GODEBUG

		} else if len(p.CgoFiles) > 0 {
			src = p.CgoFiles[0]
		} else {
			// this case could only happen if the provided source uses cgo
			// while cgo is disabled.
			hint := ""
			if !cfg.BuildContext.CgoEnabled {
				hint = " (cgo is disabled)"
			}
			base.Fatalf("go: no suitable source files%s", hint)
		}
		p.Internal.ExeName = src[:len(src)-len(".go")]
	} else {
		p.Internal.ExeName = path.Base(p.ImportPath)

		"builtin": true, // ignore pseudo-package that exists only for documentation
	}
	addPkg := func(p string) {
		mu.Lock()
		m.Pkgs = append(m.Pkgs, p)
		mu.Unlock()
	}
	if !cfg.BuildContext.CgoEnabled {
		have["runtime/cgo"] = true // ignore during walk
	}

	type pruning int8
	const (
		pruneVendor = pruning(1 << iota)
		pruneGoMod
	)

	q := par.NewQueue(runtime.GOMAXPROCS(0))

		env = append(env, "TESTGOVCS=panic")
	}

	if os.Getenv("CGO_ENABLED") != "" || runtime.GOOS != goHostOS || runtime.GOARCH != goHostArch {
		// If the actual CGO_ENABLED might not match the cmd/go default, set it
		// explicitly in the environment. Otherwise, leave it unset so that we also
		// cover the default behaviors.
		env = append(env, "CGO_ENABLED="+cgoEnabled)
	}

	for _, key := range extraEnvKeys {

	if !cfg.BuildContext.CgoEnabled && (cfg.Goos != "darwin" || cfg.BuildASan || cfg.BuildMSan) {
		if runtime.GOOS != cfg.Goos || runtime.GOARCH != cfg.Goarch {
			fmt.Fprintf(os.Stderr, "go: %s requires cgo\n", modeFlag)
		} else {
			fmt.Fprintf(os.Stderr, "go: %s requires cgo; enable cgo by setting CGO_ENABLED=1\n", modeFlag)
		}

		base.SetExitStatus(2)
		base.Exit()
	}

	}

	return pkg, nil
}

// pkgFilenames returns the list of package filenames for the given directory.
func pkgFilenames(dir string, includeTest bool) ([]string, error) {
	ctxt := build.Default
	ctxt.CgoEnabled = false
	pkg, err := ctxt.ImportDir(dir, 0)
	if err != nil {
		if _, nogo := err.(*build.NoGoError); nogo {
			return nil, nil // no *.go files, not an error
		}
		return nil, err
	}

	// to locate the main module.
	//
	// If Dir is non-empty, directories passed to Import and ImportDir must
	// be absolute.
	Dir string

	CgoEnabled  bool   // whether cgo files are included
	UseAllFiles bool   // use files regardless of //go:build lines, file names
	Compiler    string // compiler to assume when computing target paths