* run go linters for static code checking

* fix(lint): fix all goimports linting errors

* fix(lint): fix all golint errors

* fix(lint): fix all spelling errors
Co-authored-by: Aaron U'Ren <aauren@gmail.com>

* Makefile: Add lint using golangci-lint

* build/travis-test.sh: Run lint step

* metrics_controller: Lint

pkg/metrics/metrics_controller.go:150:2: `mu` is unused (structcheck)
        mu          sync.Mutex
        ^
pkg/metrics/metrics_controller.go:151:2: `nodeIP` is unused (structcheck)
        nodeIP      net.IP
        ^

* network_service_graceful: Lint

pkg/controllers/proxy/network_service_graceful.go:21:6: `gracefulQueueItem` is unused (deadcode)
type gracefulQueueItem struct {
     ^
pkg/controllers/proxy/network_service_graceful.go:22:2: `added` is unused (structcheck)
        added   time.Time
        ^
pkg/controllers/proxy/network_service_graceful.go:23:2: `service` is unused (structcheck)
        service *ipvs.Service
        ^

* network_services_controller_test: Lint

pkg/controllers/proxy/network_services_controller_test.go:80:6: func `logf` is unused (unused)

* ecmp_vip: Lint

pkg/controllers/routing/ecmp_vip.go:208:4: S1023: redundant `return` statement (gosimple)
                        return
                        ^

* bgp_peers: Lint

pkg/controllers/routing/bgp_peers.go:331:4: S1023: redundant `return` statement (gosimple)
                        return
                        ^

* bgp_policies: Lint

pkg/controllers/routing/bgp_policies.go:80:3: S1011: should replace loop with `externalBgpPeers = append(externalBgpPeers, nrc.nodePeerRouters...)` (gosimple)
                for _, peer := range nrc.nodePeerRouters {
                ^
pkg/controllers/routing/bgp_policies.go:23:20: ineffectual assignment to `err` (ineffassign)
        podCidrPrefixSet, err := table.NewPrefixSet(config.PrefixSet{
                          ^
pkg/controllers/routing/bgp_policies.go:42:22: ineffectual assignment to `err` (ineffassign)
        clusterIPPrefixSet, err := table.NewPrefixSet(config.PrefixSet{
                            ^
pkg/controllers/routing/bgp_policies.go:33:30: Error return value of `nrc.bgpServer.AddDefinedSet` is not checked (errcheck)
                nrc.bgpServer.AddDefinedSet(podCidrPrefixSet)
                                           ^
pkg/controllers/routing/bgp_policies.go:48:30: Error return value of `nrc.bgpServer.AddDefinedSet` is not checked (errcheck)
                nrc.bgpServer.AddDefinedSet(clusterIPPrefixSet)
                                           ^
pkg/controllers/routing/bgp_policies.go:69:31: Error return value of `nrc.bgpServer.AddDefinedSet` is not checked (errcheck)
                        nrc.bgpServer.AddDefinedSet(iBGPPeerNS)
                                                   ^
pkg/controllers/routing/bgp_policies.go:108:31: Error return value of `nrc.bgpServer.AddDefinedSet` is not checked (errcheck)
                        nrc.bgpServer.AddDefinedSet(ns)
                                                   ^
pkg/controllers/routing/bgp_policies.go:120:30: Error return value of `nrc.bgpServer.AddDefinedSet` is not checked (errcheck)
                nrc.bgpServer.AddDefinedSet(ns)
                                           ^
                                                   ^

* network_policy_controller: Lint

pkg/controllers/netpol/network_policy_controller.go:35:2: `networkPolicyAnnotation` is unused (deadcode)
        networkPolicyAnnotation      = "net.beta.kubernetes.io/network-policy"
        ^
pkg/controllers/netpol/network_policy_controller.go:1047:4: SA9003: empty branch (staticcheck)
                        if err != nil {
                        ^
pkg/controllers/netpol/network_policy_controller.go:969:10: SA4006: this value of `err` is never used (staticcheck)
        chains, err := iptablesCmdHandler.ListChains("filter")
                ^
pkg/controllers/netpol/network_policy_controller.go:1568:4: SA4006: this value of `err` is never used (staticcheck)
                        err = iptablesCmdHandler.Delete("filter", "FORWARD", strconv.Itoa(i-realRuleNo))
                        ^
pkg/controllers/netpol/network_policy_controller.go:1584:4: SA4006: this value of `err` is never used (staticcheck)
                        err = iptablesCmdHandler.Delete("filter", "OUTPUT", strconv.Itoa(i-realRuleNo))
                        ^

* network_services_controller: Lint

pkg/controllers/proxy/network_services_controller.go:66:2: `h` is unused (deadcode)
        h      *ipvs.Handle
        ^
pkg/controllers/proxy/network_services_controller.go:879:23: SA1019: client.NewEnvClient is deprecated: use NewClientWithOpts(FromEnv)  (staticcheck)
        dockerClient, err := client.NewEnvClient()
                             ^
pkg/controllers/proxy/network_services_controller.go:944:5: unreachable: unreachable code (govet)
                                glog.V(3).Infof("Waiting for tunnel interface %s to come up in the pod, retrying", KUBE_TUNNEL_IF)
                                ^
pkg/controllers/proxy/network_services_controller.go:1289:5: S1002: should omit comparison to bool constant, can be simplified to `!hasHairpinChain` (gosimple)
        if hasHairpinChain != true {
           ^
pkg/controllers/proxy/network_services_controller.go:1237:43: S1019: should use make(map[string][]string) instead (gosimple)
        rulesNeeded := make(map[string][]string, 0)
                                                 ^
pkg/controllers/proxy/network_services_controller.go:1111:4: S1023: redundant break statement (gosimple)
                        break
                        ^
pkg/controllers/proxy/network_services_controller.go:1114:4: S1023: redundant break statement (gosimple)
                        break
                        ^
pkg/controllers/proxy/network_services_controller.go:1117:4: S1023: redundant break statement (gosimple)
                        break
                        ^
pkg/controllers/proxy/network_services_controller.go:445:21: Error return value of `nsc.publishMetrics` is not checked (errcheck)
                nsc.publishMetrics(nsc.serviceMap)
                                  ^
pkg/controllers/proxy/network_services_controller.go:1609:9: Error return value of `h.Write` is not checked (errcheck)
        h.Write([]byte(ip + "-" + protocol + "-" + port))
               ^
pkg/controllers/proxy/network_services_controller.go:912:13: Error return value of `netns.Set` is not checked (errcheck)
                        netns.Set(hostNetworkNamespaceHandle)
                                 ^
pkg/controllers/proxy/network_services_controller.go:926:13: Error return value of `netns.Set` is not checked (errcheck)
                        netns.Set(hostNetworkNamespaceHandle)
                                 ^
pkg/controllers/proxy/network_services_controller.go:950:13: Error return value of `netns.Set` is not checked (errcheck)
                        netns.Set(hostNetworkNamespaceHandle)
                                 ^
pkg/controllers/proxy/network_services_controller.go:641:9: SA4006: this value of `err` is never used (staticcheck)
        addrs, err := getAllLocalIPs()
               ^

* network_routes_controller: Lint

pkg/controllers/routing/network_routes_controller.go:340:2: S1000: should use for range instead of for { select {} } (gosimple)
        for {
        ^
pkg/controllers/routing/network_routes_controller.go:757:22: Error return value of `nrc.bgpServer.Stop` is not checked (errcheck)
                        nrc.bgpServer.Stop()
                                          ^
pkg/controllers/routing/network_routes_controller.go:770:22: Error return value of `nrc.bgpServer.Stop` is not checked (errcheck)
                        nrc.bgpServer.Stop()
                                          ^
pkg/controllers/routing/network_routes_controller.go:782:23: Error return value of `nrc.bgpServer.Stop` is not checked (errcheck)
                                nrc.bgpServer.Stop()
                                                  ^
pkg/controllers/routing/network_routes_controller.go:717:12: Error return value of `g.Serve` is not checked (errcheck)
        go g.Serve()

* ipset: Lint

pkg/utils/ipset.go:243:23: Error return value of `entry.Set.Parent.Save` is not checked (errcheck)
        entry.Set.Parent.Save()
                             ^

* pkg/cmd/kube-router: Lint

pkg/cmd/kube-router.go:214:26: SA1006: printf-style function with dynamic format string and no further arguments should use print-style function instead (staticcheck)
                fmt.Fprintf(os.Stderr, output)
                                       ^
pkg/cmd/kube-router.go:184:15: SA1017: the channel used with signal.Notify should be buffered (staticcheck)
        signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
                     ^
pkg/cmd/kube-router.go:94:17: Error return value of `hc.RunServer` is not checked (errcheck)
        go hc.RunServer(stopCh, &wg)
                       ^
pkg/cmd/kube-router.go:112:16: Error return value of `hc.RunCheck` is not checked (errcheck)
        go hc.RunCheck(healthChan, stopCh, &wg)
                      ^
pkg/cmd/kube-router.go:121:12: Error return value of `mc.Run` is not checked (errcheck)
                go mc.Run(healthChan, stopCh, &wg)
                         ^

* cmd/kube-router/kube-router: Lint

cmd/kube-router/kube-router.go:31:24: Error return value of `flag.CommandLine.Parse` is not checked (errcheck)
        flag.CommandLine.Parse([]string{})
                              ^
cmd/kube-router/kube-router.go:33:10: Error return value of `flag.Set` is not checked (errcheck)
        flag.Set("logtostderr", "true")
                ^
cmd/kube-router/kube-router.go:34:10: Error return value of `flag.Set` is not checked (errcheck)
        flag.Set("v", config.VLevel)
                ^
cmd/kube-router/kube-router.go:62:27: SA1006: printf-style function with dynamic format string and no further arguments should use print-style function instead (staticcheck)
                        fmt.Fprintf(os.Stdout, http.ListenAndServe("0.0.0.0:6060", nil).Error())
                                               ^

* kube-router_test: Lint

cmd/kube-router/kube-router_test.go:21:10: Error return value of `io.Copy` is not checked (errcheck)
                io.Copy(stderrBuf, stderrR)
                       ^
cmd/kube-router/kube-router_test.go:40:17: Error return value of `docBuf.ReadFrom` is not checked (errcheck)
        docBuf.ReadFrom(docF)
                       ^

* service_endpoints_sync: Lint

pkg/controllers/proxy/service_endpoints_sync.go:460:2: ineffectual assignment to `ipvsSvcs` (ineffassign)
        ipvsSvcs, err := nsc.ln.ipvsGetServices()
        ^
pkg/controllers/proxy/service_endpoints_sync.go:311:5: SA4006: this value of `err` is never used (staticcheck)
                                err = nsc.ln.ipAddrDel(dummyVipInterface, externalIP)
                                ^

* node: Lint

pkg/utils/node.go:19:16: SA1019: clientset.Core is deprecated: please explicitly pick a version if possible.  (staticcheck)
                node, err := clientset.Core().Nodes().Get(nodeName, metav1.GetOptions{})
                             ^
pkg/utils/node.go:27:15: SA1019: clientset.Core is deprecated: please explicitly pick a version if possible.  (staticcheck)
        node, err := clientset.Core().Nodes().Get(hostName, metav1.GetOptions{})
                     ^
pkg/utils/node.go:34:15: SA1019: clientset.Core is deprecated: please explicitly pick a version if possible.  (staticcheck)
                node, err = clientset.Core().Nodes().Get(hostnameOverride, metav1.GetOptions{})
                            ^

* aws: Lint

pkg/controllers/routing/aws.go:31:8: SA4006: this value of `err` is never used (staticcheck)
                URL, err := url.Parse(providerID)
                     ^

* health_controller: Lint

pkg/healthcheck/health_controller.go:54:10: Error return value of `w.Write` is not checked (errcheck)
                w.Write([]byte("OK\n"))
                       ^
pkg/healthcheck/health_controller.go:68:10: Error return value of `w.Write` is not checked (errcheck)
                w.Write([]byte("Unhealthy"))
                       ^
pkg/healthcheck/health_controller.go:159:2: S1000: should use a simple channel send/receive instead of `select` with a single case (gosimple)
        select {
        ^

* network_routes_controller_test: Lint

pkg/controllers/routing/network_routes_controller_test.go:1113:37: Error return value of `testcase.nrc.bgpServer.Stop` is not checked (errcheck)
                        defer testcase.nrc.bgpServer.Stop()
                                                         ^
pkg/controllers/routing/network_routes_controller_test.go:1314:37: Error return value of `testcase.nrc.bgpServer.Stop` is not checked (errcheck)
                        defer testcase.nrc.bgpServer.Stop()
                                                         ^
pkg/controllers/routing/network_routes_controller_test.go:2327:37: Error return value of `testcase.nrc.bgpServer.Stop` is not checked (errcheck)
                        defer testcase.nrc.bgpServer.Stop()
                                                         ^

* .golangci.yml: Increase timeout

Default is 1m, increase to 5m otherwise travis might fail

* Makefile: Update golangci-lint to 1.27.0

* kube-router_test.go: defer waitgroup
Co-authored-by: Aaron U'Ren <aauren@users.noreply.github.com>

* network_routes_controller: Incorporate review

* bgp_policies: Incorporate review

* network_routes_controller: Incorporate review

* bgp_policies: Log error instead

* network_services_controller: Incorporate review
Co-authored-by: Aaron U'Ren <aauren@users.noreply.github.com>