// directory instead. (That can occur, for example, when running under
	// run.bash with GO_TEST_SHORT=0: run.bash sets GOPATH=/nonexist-gopath, and
	// GO_TEST_SHORT=0 causes it to run this portion of the test.)
	var modcacheEnv []string
	{
		out, err := testenv.Command(t, goBin, "env", "GOMODCACHE").Output()
		if err != nil {
			t.Fatalf("%s env GOMODCACHE: %v", goBin, err)
		}
		modcacheOk := false