func main()

in mockgen/mockgen.go [68:177]
93 lines of code
23 McCabe index (conditional complexity)

func main() {
	flag.Usage = usage
	flag.Parse()

	if *showVersion {
		printVersion()
		return
	}

	var pkg *model.Package
	var err error
	var packageName string
	if *source != "" {
		pkg, err = sourceMode(*source)
	} else {
		if flag.NArg() != 2 {
			usage()
			log.Fatal("Expected exactly two arguments")
		}
		packageName = flag.Arg(0)
		interfaces := strings.Split(flag.Arg(1), ",")
		if packageName == "." {
			dir, err := os.Getwd()
			if err != nil {
				log.Fatalf("Get current directory failed: %v", err)
			}
			packageName, err = packageNameOfDir(dir)
			if err != nil {
				log.Fatalf("Parse package name failed: %v", err)
			}
		}
		pkg, err = reflectMode(packageName, interfaces)
	}
	if err != nil {
		log.Fatalf("Loading input failed: %v", err)
	}

	if *debugParser {
		pkg.Print(os.Stdout)
		return
	}

	dst := os.Stdout
	if len(*destination) > 0 {
		if err := os.MkdirAll(filepath.Dir(*destination), os.ModePerm); err != nil {
			log.Fatalf("Unable to create directory: %v", err)
		}
		f, err := os.Create(*destination)
		if err != nil {
			log.Fatalf("Failed opening destination file: %v", err)
		}
		defer f.Close()
		dst = f
	}

	outputPackageName := *packageOut
	if outputPackageName == "" {
		// pkg.Name in reflect mode is the base name of the import path,
		// which might have characters that are illegal to have in package names.
		outputPackageName = "mock_" + sanitize(pkg.Name)
	}

	// outputPackagePath represents the fully qualified name of the package of
	// the generated code. Its purposes are to prevent the module from importing
	// itself and to prevent qualifying type names that come from its own
	// package (i.e. if there is a type called X then we want to print "X" not
	// "package.X" since "package" is this package). This can happen if the mock
	// is output into an already existing package.
	outputPackagePath := *selfPackage
	if outputPackagePath == "" && *destination != "" {
		dstPath, err := filepath.Abs(filepath.Dir(*destination))
		if err == nil {
			pkgPath, err := parsePackageImport(dstPath)
			if err == nil {
				outputPackagePath = pkgPath
			} else {
				log.Println("Unable to infer -self_package from destination file path:", err)
			}
		} else {
			log.Println("Unable to determine destination file path:", err)
		}
	}

	g := new(generator)
	if *source != "" {
		g.filename = *source
	} else {
		g.srcPackage = packageName
		g.srcInterfaces = flag.Arg(1)
	}
	g.destination = *destination

	if *mockNames != "" {
		g.mockNames = parseMockNames(*mockNames)
	}
	if *copyrightFile != "" {
		header, err := ioutil.ReadFile(*copyrightFile)
		if err != nil {
			log.Fatalf("Failed reading copyright file: %v", err)
		}

		g.copyrightHeader = string(header)
	}
	if err := g.Generate(pkg, outputPackageName, outputPackagePath); err != nil {
		log.Fatalf("Failed generating mock: %v", err)
	}
	if _, err := dst.Write(g.Output()); err != nil {
		log.Fatalf("Failed writing to destination: %v", err)
	}
}