func main()

in cmd/nginx/main.go [54:161]
84 lines of code
19 McCabe index (conditional complexity)

func main() {
	klog.InitFlags(nil)

	rand.Seed(time.Now().UnixNano())

	fmt.Println(version.String())

	showVersion, conf, err := parseFlags()
	if showVersion {
		os.Exit(0)
	}

	if err != nil {
		klog.Fatal(err)
	}

	err = file.CreateRequiredDirectories()
	if err != nil {
		klog.Fatal(err)
	}

	kubeClient, err := createApiserverClient(conf.APIServerHost, conf.RootCAFile, conf.KubeConfigFile)
	if err != nil {
		handleFatalInitError(err)
	}

	if len(conf.DefaultService) > 0 {
		err := checkService(conf.DefaultService, kubeClient)
		if err != nil {
			klog.Fatal(err)
		}

		klog.InfoS("Valid default backend", "service", conf.DefaultService)
	}

	if len(conf.PublishService) > 0 {
		err := checkService(conf.PublishService, kubeClient)
		if err != nil {
			klog.Fatal(err)
		}
	}

	if conf.Namespace != "" {
		_, err = kubeClient.CoreV1().Namespaces().Get(context.TODO(), conf.Namespace, metav1.GetOptions{})
		if err != nil {
			klog.Fatalf("No namespace with name %v found: %v", conf.Namespace, err)
		}
	}

	conf.FakeCertificate = ssl.GetFakeSSLCert()
	klog.InfoS("SSL fake certificate created", "file", conf.FakeCertificate.PemFileName)

	if !k8s.NetworkingIngressAvailable(kubeClient) {
		klog.Fatalf("ingress-nginx requires Kubernetes v1.19.0 or higher")
	}

	_, err = kubeClient.NetworkingV1().IngressClasses().List(context.TODO(), metav1.ListOptions{})
	if err != nil {
		if !errors.IsNotFound(err) {
			if errors.IsForbidden(err) {
				klog.Warningf("No permissions to list and get Ingress Classes: %v, IngressClass feature will be disabled", err)
				conf.IngressClassConfiguration.IgnoreIngressClass = true
			}
		}
	}
	conf.Client = kubeClient

	err = k8s.GetIngressPod(kubeClient)
	if err != nil {
		klog.Fatalf("Unexpected error obtaining ingress-nginx pod: %v", err)
	}

	reg := prometheus.NewRegistry()

	reg.MustRegister(prometheus.NewGoCollector())
	reg.MustRegister(prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{
		PidFn:        func() (int, error) { return os.Getpid(), nil },
		ReportErrors: true,
	}))

	mc := metric.NewDummyCollector()
	if conf.EnableMetrics {
		mc, err = metric.NewCollector(conf.MetricsPerHost, reg, conf.IngressClassConfiguration.Controller, *conf.MetricsBuckets)
		if err != nil {
			klog.Fatalf("Error creating prometheus collector:  %v", err)
		}
	}
	// Pass the ValidationWebhook status to determine if we need to start the collector
	// for the admissionWebhook
	mc.Start(conf.ValidationWebhook)

	if conf.EnableProfiling {
		go registerProfiler()
	}

	ngx := controller.NewNGINXController(conf, mc)

	mux := http.NewServeMux()
	registerHealthz(nginx.HealthPath, ngx, mux)
	registerMetrics(reg, mux)

	go startHTTPServer(conf.HealthCheckHost, conf.ListenPorts.Health, mux)
	go ngx.Start()

	handleSigterm(ngx, conf.PostShutdownGracePeriod, func(code int) {
		os.Exit(code)
	})
}