func main()

in cmd/config-downloader/downloader.go [98:229]
117 lines of code
29 McCabe index (conditional complexity)

func main() {

	defer func() {
		if r := recover(); r != nil {
			if val, ok := r.(string); ok {
				fmt.Println(val)
			}
			fmt.Println(exitErrorMessage)
			os.Exit(1)
		}
	}()

	var region, mode, downloadLocation, outputDir, inputConfig, multiConfig string

	flag.StringVar(&mode, "mode", "ec2", "Please provide the mode, i.e. ec2, onPremise, onPrem, auto")
	flag.StringVar(&downloadLocation, "download-source", "",
		"Download source. Example: \"ssm:my-parameter-store-name\" for an EC2 SSM Parameter Store Name holding your CloudWatch Agent configuration.")
	flag.StringVar(&outputDir, "output-dir", "", "Path of output json config directory.")
	flag.StringVar(&inputConfig, "config", "", "Please provide the common-config file")
	flag.StringVar(&multiConfig, "multi-config", "default", "valid values: default, append, remove")
	flag.Parse()

	cc := commonconfig.New()
	if inputConfig != "" {
		f, err := os.Open(inputConfig)
		if err != nil {
			log.Panicf("E! Failed to open Common Config: %v", err)
		}

		if err := cc.Parse(f); err != nil {
			log.Panicf("E! Failed to open Common Config: %v", err)
		}
	}
	util.SetProxyEnv(cc.ProxyMap())
	util.SetSSLEnv(cc.SSLMap())
	var errorMessage string
	if downloadLocation == "" || outputDir == "" {
		var errorMessage string
		if executable, err := os.Executable(); err == nil {
			errorMessage = "E! usage: " + filepath.Base(executable) + " --output-dir <path> --download-source ssm:<parameter-store-name>"
		} else {
			errorMessage = "E! usage: --output-dir <path> --download-source ssm:<parameter-store-name>"
		}
		log.Panic(errorMessage)
	}

	mode = sdkutil.DetectAgentMode(mode)

	region, _ = util.DetectRegion(mode, cc.CredentialsMap())

	if region == "" && downloadLocation != locationDefault {
		fmt.Println("Unable to determine aws-region.")
		if mode == config.ModeEC2 {
			errorMessage = "E! Please check if you can access the metadata service. For example, on linux, run 'wget -q -O - http://169.254.169.254/latest/meta-data/instance-id && echo' "
		} else {
			errorMessage = "E! Please make sure the credentials and region set correctly on your hosts.\n" +
				"Refer to http://docs.aws.amazon.com/cli/latest/userguide/cli-chap-getting-started.html"
		}
		log.Panic(errorMessage)
	}

	// clean up output dir for tmp files before writing out new tmp file.
	// this step cannot be in translator because it is too late at that time.
	filepath.Walk(
		outputDir,
		func(path string, info os.FileInfo, err error) error {
			if err != nil {
				fmt.Printf("Cannot access %v: %v \n", path, err)
				return err
			}
			if info.IsDir() {
				if strings.EqualFold(path, outputDir) {
					return nil
				} else {
					fmt.Printf("Sub dir %v will be ignored.", path)
					return filepath.SkipDir
				}
			}
			if filepath.Ext(path) == constants.FileSuffixTmp {
				return os.Remove(path)
			}
			return nil
		})

	locationArray := strings.SplitN(downloadLocation, locationSeparator, 2)
	if locationArray == nil || len(locationArray) < 2 && downloadLocation != locationDefault {
		log.Panicf("E! downloadLocation %s is malformated.", downloadLocation)
	}

	var config, outputFilePath string
	var err error
	switch locationArray[0] {
	case locationDefault:
		outputFilePath = locationDefault
		if multiConfig != "remove" {
			config, err = defaultJsonConfig(mode)
		}
	case locationSSM:
		outputFilePath = locationSSM + "_" + EscapeFilePath(locationArray[1])
		if multiConfig != "remove" {
			config, err = downloadFromSSM(region, locationArray[1], mode, cc.CredentialsMap())
		}
	case locationFile:
		outputFilePath = locationFile + "_" + EscapeFilePath(filepath.Base(locationArray[1]))
		if multiConfig != "remove" {
			config, err = readFromFile(locationArray[1])
		}
	default:
		log.Panicf("E! Location type %s is not supported.", locationArray[0])
	}

	if err != nil {
		log.Panicf("E! Fail to fetch/remove json config: %v", err)
	}

	if multiConfig != "remove" {
		outputFilePath = filepath.Join(outputDir, outputFilePath+constants.FileSuffixTmp)
		err = os.WriteFile(outputFilePath, []byte(config), 0644)
		if err != nil {
			log.Panicf("E! Failed to write the json file %v: %v", outputFilePath, err)
		} else {
			fmt.Printf("Successfully fetched the config and saved in %s\n", outputFilePath)
		}
	} else {
		outputFilePath = filepath.Join(outputDir, outputFilePath)
		if err := os.Remove(outputFilePath); err != nil {
			log.Panicf("E! Failed to remove the json file %v: %v", outputFilePath, err)
		} else {
			fmt.Printf("Successfully removed the config file %s\n", outputFilePath)
		}
	}
}