func main()

in cmd/buildlet/stage0/stage0.go [62:244]
148 lines of code
39 McCabe index (conditional complexity)

func main() {
	if configureSerialLogOutput != nil {
		configureSerialLogOutput()
	}
	log.SetPrefix("stage0: ")
	flag.Parse()

	if *untarFile != "" {
		log.Printf("running in untar mode, untarring %q to %q", *untarFile, *untarDestDir)
		untarMode()
		log.Printf("done untarring; exiting")
		return
	}
	log.Printf("bootstrap binary running")

	var isMacStadiumVM bool
	switch osArch {
	case "linux/arm":
		switch env := os.Getenv("GO_BUILDER_ENV"); env {
		case "host-linux-arm-aws":
			// No setup currently.
		default:
			panic(fmt.Sprintf("unknown/unspecified $GO_BUILDER_ENV value %q", env))
		}
	case "linux/arm64":
		switch env := os.Getenv("GO_BUILDER_ENV"); env {
		case "host-linux-arm64-packet", "host-linux-arm64-aws":
			// No special setup.
		default:
			panic(fmt.Sprintf("unknown/unspecified $GO_BUILDER_ENV value %q", env))
		}
	case "darwin/amd64":
		// The MacStadium builders' baked-in stage0.sh
		// bootstrap file doesn't set GO_BUILDER_ENV
		// unfortunately, so use the filename it runs its
		// downloaded bootstrap URL to determine whether we're
		// in that environment.
		isMacStadiumVM = len(os.Args) > 0 && strings.HasSuffix(os.Args[0], "run-builder")
		log.Printf("isMacStadiumVM = %v", isMacStadiumVM)
		os.Setenv("GO_BUILDER_ENV", "macstadium_vm")
	}

	if !awaitNetwork() {
		sleepFatalf("network didn't become reachable")
	}
	timeNetwork := time.Now()
	netDelay := prettyDuration(timeNetwork.Sub(timeStart))
	log.Printf("network up after %v", netDelay)

Download:
	// Note: we name it ".exe" for Windows, but the name also
	// works fine on Linux, etc.
	target := filepath.FromSlash("./buildlet.exe")
	if err := download(target, buildletURL()); err != nil {
		sleepFatalf("Downloading %s: %v", buildletURL(), err)
	}

	if runtime.GOOS != "windows" {
		if err := os.Chmod(target, 0755); err != nil {
			log.Fatal(err)
		}
	}
	downloadDelay := prettyDuration(time.Since(timeNetwork))
	log.Printf("downloaded buildlet in %v", downloadDelay)

	env := os.Environ()
	if isUnix() && os.Getuid() == 0 {
		if os.Getenv("USER") == "" {
			env = append(env, "USER=root")
		}
		if os.Getenv("HOME") == "" {
			env = append(env, "HOME=/root")
		}
	}
	env = append(env, fmt.Sprintf("GO_STAGE0_NET_DELAY=%v", netDelay))
	env = append(env, fmt.Sprintf("GO_STAGE0_DL_DELAY=%v", downloadDelay))

	cmd := exec.Command(target)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	cmd.Env = env

	// buildEnv is set by some builders. It's increasingly set by new ones.
	// It predates the buildtype-vs-hosttype split, so the values aren't
	// always host types, but they're often host types. They should probably
	// be host types in the future, or we can introduce GO_BUILD_HOST_TYPE
	// to be explicit and kill off GO_BUILDER_ENV.
	buildEnv := os.Getenv("GO_BUILDER_ENV")

	switch buildEnv {
	case "host-linux-arm-aws":
		cmd.Args = append(cmd.Args, os.ExpandEnv("--workdir=${WORKDIR}"))
	case "host-linux-arm64-aws":
		cmd.Args = append(cmd.Args, os.ExpandEnv("--workdir=${WORKDIR}"))
	case "host-linux-mipsle-mengzhuo":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
		cmd.Args = append(cmd.Args, os.ExpandEnv("--workdir=${WORKDIR}"))
	case "host-linux-loong64-3a5000":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
		cmd.Args = append(cmd.Args, os.ExpandEnv("--workdir=${WORKDIR}"))
	case "host-linux-mips64le-rtrk":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
		cmd.Args = append(cmd.Args, os.ExpandEnv("--workdir=${WORKDIR}"))
		cmd.Args = append(cmd.Args, os.ExpandEnv("--hostname=${GO_BUILDER_ENV}"))
	case "host-linux-mips64-rtrk":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
		cmd.Args = append(cmd.Args, os.ExpandEnv("--workdir=${WORKDIR}"))
		cmd.Args = append(cmd.Args, os.ExpandEnv("--hostname=${GO_BUILDER_ENV}"))
	case "host-linux-ppc64le-power9-osu":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
	case "host-linux-ppc64le-osu": // power8
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
	case "host-linux-ppc64-osu":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
	case "host-linux-amd64-wsl":
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(buildEnv)...)
	}
	switch osArch {
	case "linux/s390x":
		cmd.Args = append(cmd.Args, "--workdir=/data/golang/workdir")
		cmd.Args = append(cmd.Args, reverseHostTypeArgs("host-linux-s390x")...)
	case "linux/arm64":
		switch buildEnv {
		case "host-linux-arm64-packet":
			hostname := os.Getenv("HOSTNAME") // if empty, docker container name is used
			cmd.Args = append(cmd.Args,
				"--reverse-type="+buildEnv,
				"--workdir=/workdir",
				"--hostname="+hostname,
				"--halt=false",
				"--reboot=false",
				"--coordinator=farmer.golang.org:443",
			)
		case "host-linux-arm64-aws":
			// no special configuration
		default:
			panic(fmt.Sprintf("unknown/unspecified $GO_BUILDER_ENV value %q", env))
		}
	case "solaris/amd64", "illumos/amd64":
		hostType := buildEnv
		cmd.Args = append(cmd.Args, reverseHostTypeArgs(hostType)...)
	case "windows/arm64":
		switch buildEnv {
		case "host-windows-arm64-mini", "host-windows11-arm64-mini":
			cmd.Args = append(cmd.Args,
				"--halt=true",
				"--reverse-type="+buildEnv,
				"--coordinator=farmer.golang.org:443",
			)
		}
	}
	// Release the serial port (if we opened it) so the buildlet
	// process can open & write to it. At least on Windows, only
	// one process can have it open.
	if closeSerialLogOutput != nil {
		closeSerialLogOutput()
	}
	err := cmd.Run()
	if isMacStadiumVM {
		if err != nil {
			log.Printf("error running buildlet: %v", err)
			log.Printf("restarting in 2 seconds.")
			time.Sleep(2 * time.Second) // in case we're spinning, slow it down
		} else {
			log.Printf("buildlet process exited; restarting.")
		}
		// Some of the MacStadium VM environments reuse their
		// environment. Re-download the buildlet (if it
		// changed-- httpdl does conditional downloading) and
		// then re-run. At least on Sierra we never get this
		// far because the buildlet will halt the machine
		// before we get here. (and then cmd/makemac will
		// recreate the VM)
		// But if we get here, restart the process.
		goto Download
	}
	if err != nil {
		if configureSerialLogOutput != nil {
			configureSerialLogOutput()
		}
		sleepFatalf("Error running buildlet: %v", err)
	}
}