func main()

in cmd/frontend/main.go [49:193]
133 lines of code
18 McCabe index (conditional complexity)

func main() {
	flag.Parse()
	ctx := context.Background()
	cfg, err := config.Init(ctx)
	if err != nil {
		log.Fatal(ctx, err)
	}
	cfg.Dump(os.Stderr)
	if cfg.UseProfiler {
		if err := profiler.Start(profiler.Config{}); err != nil {
			log.Fatalf(ctx, "profiler.Start: %v", err)
		}
	}

	var (
		dsg        func(context.Context) internal.DataSource
		fetchQueue queue.Queue
	)
	if *bypassLicenseCheck {
		log.Info(ctx, "BYPASSING LICENSE CHECKING: DISPLAYING NON-REDISTRIBUTABLE INFORMATION")
	}

	log.Infof(ctx, "cmd/frontend: initializing cmdconfig.ExperimentGetter")
	expg := cmdconfig.ExperimentGetter(ctx, cfg)
	log.Infof(ctx, "cmd/frontend: initialized cmdconfig.ExperimentGetter")

	proxyClient, err := proxy.New(*proxyURL)
	if err != nil {
		log.Fatal(ctx, err)
	}

	if *directProxy {
		ds := fetchdatasource.Options{
			Getters:              []fetch.ModuleGetter{fetch.NewProxyModuleGetter(proxyClient, source.NewClient(1*time.Minute))},
			ProxyClientForLatest: proxyClient,
			BypassLicenseCheck:   *bypassLicenseCheck,
		}.New()
		dsg = func(context.Context) internal.DataSource { return ds }
	} else {
		db, err := cmdconfig.OpenDB(ctx, cfg, *bypassLicenseCheck)
		if err != nil {
			log.Fatalf(ctx, "%v", err)
		}
		defer db.Close()
		dsg = func(context.Context) internal.DataSource { return db }
		sourceClient := source.NewClient(config.SourceTimeout)
		// The closure passed to queue.New is only used for testing and local
		// execution, not in production. So it's okay that it doesn't use a
		// per-request connection.
		fetchQueue, err = queue.New(ctx, cfg, queueName, *workers, expg,
			func(ctx context.Context, modulePath, version string) (int, error) {
				return frontend.FetchAndUpdateState(ctx, modulePath, version, proxyClient, sourceClient, db)
			})
		if err != nil {
			log.Fatalf(ctx, "queue.New: %v", err)
		}
	}

	rc := cmdconfig.ReportingClient(ctx, cfg)
	vc, err := vulnc.NewClient([]string{cfg.VulnDB}, vulnc.Options{
		HTTPCache: newVulndbCache(),
	})
	if err != nil {
		log.Fatalf(ctx, "vulndbc.NewClient: %v", err)
	}
	staticSource := template.TrustedSourceFromFlag(flag.Lookup("static").Value)
	server, err := frontend.NewServer(frontend.ServerConfig{
		Config:               cfg,
		DataSourceGetter:     dsg,
		Queue:                fetchQueue,
		TaskIDChangeInterval: config.TaskIDChangeIntervalFrontend,
		TemplateFS:           template.TrustedFSFromTrustedSource(staticSource),
		StaticFS:             os.DirFS(*staticFlag),
		StaticPath:           *staticFlag,
		ThirdPartyFS:         os.DirFS(*thirdPartyPath),
		DevMode:              *devMode,
		ReportingClient:      rc,
		VulndbClient:         vc,
	})
	if err != nil {
		log.Fatalf(ctx, "frontend.NewServer: %v", err)
	}

	router := dcensus.NewRouter(frontend.TagRoute)
	var cacheClient *redis.Client
	if cfg.RedisCacheHost != "" {
		addr := cfg.RedisCacheHost + ":" + cfg.RedisCachePort
		cacheClient = redis.NewClient(&redis.Options{Addr: addr})
		if err := cacheClient.Ping(ctx).Err(); err != nil {
			log.Errorf(ctx, "redis at %s: %v", addr, err)
		} else {
			log.Infof(ctx, "connected to redis at %s", addr)
		}
	}
	server.Install(router.Handle, cacheClient, cfg.AuthValues)
	views := append(dcensus.ServerViews,
		postgres.SearchLatencyDistribution,
		postgres.SearchResponseCount,
		frontend.FetchLatencyDistribution,
		frontend.FetchResponseCount,
		frontend.VersionTypeCount,
		middleware.CacheResultCount,
		middleware.CacheErrorCount,
		middleware.CacheLatency,
		middleware.QuotaResultCount,
	)
	if err := dcensus.Init(cfg, views...); err != nil {
		log.Fatal(ctx, err)
	}
	// We are not currently forwarding any ports on AppEngine, so serving debug
	// information is broken.
	if !cfg.OnAppEngine() {
		dcensusServer, err := dcensus.NewServer()
		if err != nil {
			log.Fatal(ctx, err)
		}
		go http.ListenAndServe(cfg.DebugAddr("localhost:8081"), dcensusServer)
	}
	panicHandler, err := server.PanicHandler()
	if err != nil {
		log.Fatal(ctx, err)
	}
	log.Infof(ctx, "cmd/frontend: initializing cmdconfig.Experimenter")
	experimenter := cmdconfig.Experimenter(ctx, cfg, expg, rc)
	log.Infof(ctx, "cmd/frontend: initialized cmdconfig.Experimenter")

	ermw := middleware.Identity()
	if rc != nil {
		ermw = middleware.ErrorReporting(rc.Report)
	}
	mw := middleware.Chain(
		middleware.RequestLog(cmdconfig.Logger(ctx, cfg, "frontend-log")),
		middleware.AcceptRequests(http.MethodGet, http.MethodPost, http.MethodHead), // accept only GETs, POSTs and HEADs
		middleware.BetaPkgGoDevRedirect(),
		middleware.Quota(cfg.Quota, cacheClient),
		middleware.SecureHeaders(!*disableCSP), // must come before any caching for nonces to work
		middleware.Experiment(experimenter),
		middleware.Panic(panicHandler),
		ermw,
		middleware.Timeout(54*time.Second),
	)
	addr := cfg.HostAddr(*hostAddr)
	log.Infof(ctx, "Listening on addr %s", addr)
	log.Fatal(ctx, http.ListenAndServe(addr, mw(router)))
}