if os.Getenv("CMDGO_TEST_RUN_MAIN") != "" {
		cfg.SetGOROOT(cfg.GOROOT, true)
		gover.TestVersion = os.Getenv("TESTGO_VERSION")
		toolchain.TestVersionSwitch = os.Getenv("TESTGO_VERSION_SWITCH")
		if v := os.Getenv("TESTGO_TOOLCHAIN_VERSION"); v != "" {
			work.ToolchainVersion = v
		}

		if testGOROOT := os.Getenv("TESTGO_GOROOT"); testGOROOT != "" {
			// Disallow installs to the GOROOT from which testgo was built.