Fix go fmt, go lint, and go vet issues (#494)

This fix fixes several `go fmt`, `go lint`, and `go vet` issues,
to make goreportcard happy:

https://goreportcard.com/report/github.com/miekg/coredns

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

middleware/kubernetes/kubernetes.go

@@ -44,10 +44,14 @@ type Kubernetes struct {
 }
 
 const (
-	PodModeDisabled  = "disabled" // default. pod requests are ignored
+	// PodModeDisabled is the default value where pod requests are ignored
-	PodModeVerified  = "verified" // Pod requests are answered only if they exist
+	PodModeDisabled = "disabled"
-	PodModeInsecure  = "insecure" // ALL pod requests are answered without verfying they exist
+	// PodModeVerified is where Pod requests are answered only if they exist
-	DnsSchemaVersion = "1.0.0"    // https://github.com/kubernetes/dns/blob/master/docs/specification.md
+	PodModeVerified = "verified"
+	// PodModeInsecure is where pod requests are answered without verfying they exist
+	PodModeInsecure = "insecure"
+	// DNSSchemaVersion is the schema version: https://github.com/kubernetes/dns/blob/master/docs/specification.md
+	DNSSchemaVersion = "1.0.0"
 )
 
 type endpoint struct {
@@ -100,7 +104,7 @@ func (k *Kubernetes) recordsForTXT(r recordRequest) ([]msg.Service, error) {
 	switch r.typeName {
 	case "dns-version":
 		s := msg.Service{
-			Text: DnsSchemaVersion,
+			Text: DNSSchemaVersion,
 			TTL:  28800,
 			Key:  msg.Path(r.typeName+"."+r.zone, "coredns")}
 		return []msg.Service{s}, nil
@@ -289,7 +293,7 @@ func (k *Kubernetes) Records(r recordRequest) ([]msg.Service, error) {
 		return nil, errNsNotExposed
 	}
 
-	services, pods, err := k.Get(r)
+	services, pods, err := k.get(r)
 	if err != nil {
 		return nil, err
 	}
@@ -405,8 +409,8 @@ func (k *Kubernetes) findPods(namespace, podname string) (pods []pod, err error)
 	return pods, nil
 }
 
-// Get retrieves matching data from the cache.
+// get retrieves matching data from the cache.
-func (k *Kubernetes) Get(r recordRequest) (services []service, pods []pod, err error) {
+func (k *Kubernetes) get(r recordRequest) (services []service, pods []pod, err error) {
 	switch {
 	case r.typeName == "pod":
 		pods, err = k.findPods(r.namespace, r.service)
@@ -497,7 +501,7 @@ func (k *Kubernetes) getServiceRecordForIP(ip, name string) []msg.Service {
 		}
 		if service.Spec.ClusterIP == ip {
 			domain := service.Name + "." + service.Namespace + ".svc." + k.PrimaryZone()
-			return []msg.Service{msg.Service{Host: domain}}
+			return []msg.Service{{Host: domain}}
 		}
 	}
 	// If no cluster ips match, search endpoints
@@ -513,7 +517,7 @@ func (k *Kubernetes) getServiceRecordForIP(ip, name string) []msg.Service {
 			for _, addr := range eps.Addresses {
 				if addr.IP == ip {
 					domain := endpointHostname(addr) + "." + ep.ObjectMeta.Name + "." + ep.ObjectMeta.Namespace + ".svc." + k.PrimaryZone()
-					return []msg.Service{msg.Service{Host: domain}}
+					return []msg.Service{{Host: domain}}
 				}
 			}
 		}

middleware/kubernetes/kubernetes_test.go

@@ -27,8 +27,8 @@ func TestSymbolContainsWildcard(t *testing.T) {
 
 func expectString(t *testing.T, function, qtype, query string, r *recordRequest, field, expected string) {
 	ref := reflect.ValueOf(r)
-	ref_f := reflect.Indirect(ref).FieldByName(field)
+	refField := reflect.Indirect(ref).FieldByName(field)
-	got := ref_f.String()
+	got := refField.String()
 	if got != expected {
 		t.Errorf("Expected %v(%v, \"%v\") to get %v == \"%v\". Instead got \"%v\".", function, query, qtype, field, expected, got)
 	}

middleware/pkg/tls/tls_test.go

@@ -1,8 +1,8 @@
 package tls
 
 import (
-        "testing"
 	"path/filepath"
+	"testing"
 
 	"github.com/miekg/coredns/middleware/test"
 )

middleware/trace/trace.go

@@ -52,10 +52,12 @@ func (t *Trace) setupZipkin() error {
 	return nil
 }
 
-func (t *Trace) Name() (string) {
+// Name implements the Handler interface.
+func (t *Trace) Name() string {
 	return "trace"
 }
 
+// ServeDNS implements the middleware.Handle interface.
 func (t *Trace) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
 	span := t.Tracer.StartSpan("servedns")
 	defer span.Finish()

test/etcd_test.go

@@ -70,7 +70,7 @@ func TestEtcdStubAndProxyLookup(t *testing.T) {
 	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
 	resp, err := p.Lookup(state, "example.com.", dns.TypeA)
 	if err != nil {
-		t.Fatalf("Expected to receive reply, but didn't", err)
+		t.Fatalf("Expected to receive reply, but didn't: %v", err)
 	}
 	if len(resp.Answer) == 0 {
 		t.Fatalf("Expected to at least one RR in the answer section, got none")
@@ -79,7 +79,7 @@ func TestEtcdStubAndProxyLookup(t *testing.T) {
 		t.Errorf("Expected RR to A, got: %d", resp.Answer[0].Header().Rrtype)
 	}
 	if resp.Answer[0].(*dns.A).A.String() != "93.184.216.34" {
-		t.Errorf("Expected 93.184.216.34, got: %d", resp.Answer[0].(*dns.A).A.String())
+		t.Errorf("Expected 93.184.216.34, got: %s", resp.Answer[0].(*dns.A).A.String())
 	}
 }