Enable stylecheck linter and resolve found issues.

Signed-off-by: Xun Jiang <blackpiglet@gmail.com>

pkg/cmd/cli/backup/describe.go

@@ -61,7 +61,7 @@ func NewDescribeCommand(f client.Factory, use string) *cobra.Command {
 			cmd.CheckError(err)
 
 			if outputFormat != "plaintext" && outputFormat != "json" {
-				cmd.CheckError(fmt.Errorf("Invalid output format '%s'. Valid value are 'plaintext, json'", outputFormat))
+				cmd.CheckError(fmt.Errorf("invalid output format '%s'. valid value are 'plaintext, json'", outputFormat))
 			}
 
 			var backups *velerov1api.BackupList

pkg/cmd/cli/delete_options.go

@@ -58,7 +58,7 @@ func (o *DeleteOptions) Complete(f client.Factory, args []string) error {
 // Validate validates the fields of the DeleteOptions struct.
 func (o *DeleteOptions) Validate(c *cobra.Command, f client.Factory, args []string) error {
 	if o.Client == nil {
-		return errors.New("Velero client is not set; unable to proceed")
+		return errors.New("velero client is not set; unable to proceed")
 	}
 
 	return o.SelectOptions.Validate()

pkg/cmd/cli/nodeagent/server_test.go

@@ -23,7 +23,6 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	corev1 "k8s.io/api/core/v1"
-	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes/fake"
 
@@ -51,7 +50,7 @@ func Test_validatePodVolumesHostPath(t *testing.T) {
 			name: "no error when pod volumes are present and there are mirror pods",
 			pods: []*corev1.Pod{
 				builder.ForPod("foo", "bar").ObjectMeta(builder.WithUID("foo")).Result(),
-				builder.ForPod("zoo", "raz").ObjectMeta(builder.WithUID("zoo"), builder.WithAnnotations(v1.MirrorPodAnnotationKey, "baz")).Result(),
+				builder.ForPod("zoo", "raz").ObjectMeta(builder.WithUID("zoo"), builder.WithAnnotations(corev1.MirrorPodAnnotationKey, "baz")).Result(),
 			},
 			dirs:    []string{"foo", "baz"},
 			wantErr: false,

pkg/cmd/cli/serverstatus/server_status.go

@@ -22,7 +22,6 @@ import (
 
 	"github.com/pkg/errors"
 	"k8s.io/apimachinery/pkg/util/wait"
-	"sigs.k8s.io/controller-runtime/pkg/client"
 	kbclient "sigs.k8s.io/controller-runtime/pkg/client"
 
 	velerov1api "github.com/vmware-tanzu/velero/pkg/apis/velero/v1"
@@ -48,7 +47,7 @@ func (g *DefaultServerStatusGetter) GetServerStatus(kbClient kbclient.Client) (*
 	ctx, cancel := context.WithCancel(g.Context)
 	defer cancel()
 
-	key := client.ObjectKey{Name: created.Name, Namespace: g.Namespace}
+	key := kbclient.ObjectKey{Name: created.Name, Namespace: g.Namespace}
 	checkFunc := func() {
 		updated := &velerov1api.ServerStatusRequest{}
 		if err := kbClient.Get(ctx, key, updated); err != nil {

pkg/cmd/util/downloadrequest/downloadrequest.go

@@ -60,11 +60,11 @@ func Stream(ctx context.Context, kbClient kbclient.Client, namespace, name strin
 
 	key := kbclient.ObjectKey{Name: created.Name, Namespace: namespace}
 	timeStreamFirstCheck := time.Now()
-	downloadUrlTimeout := false
+	downloadURLTimeout := false
 	checkFunc := func() {
 		// if timeout has been reached, cancel request
 		if time.Now().After(timeStreamFirstCheck.Add(timeout)) {
-			downloadUrlTimeout = true
+			downloadURLTimeout = true
 			cancel()
 		}
 		updated := &velerov1api.DownloadRequest{}
@@ -85,7 +85,7 @@ func Stream(ctx context.Context, kbClient kbclient.Client, namespace, name strin
 	}
 
 	wait.Until(checkFunc, 25*time.Millisecond, ctx.Done())
-	if downloadUrlTimeout {
+	if downloadURLTimeout {
 		return ErrDownloadRequestDownloadURLTimeout
 	}
 

pkg/cmd/util/output/describe.go

@@ -149,7 +149,7 @@ func NewStructuredDescriber(format string) *StructuredDescriber {
 func DescribeInSF(fn func(d *StructuredDescriber), format string) string {
 	d := NewStructuredDescriber(format)
 	fn(d)
-	return d.JsonEncode()
+	return d.JSONEncode()
 }
 
 // Describe adds all types of argument to d.output.
@@ -167,8 +167,8 @@ func (d *StructuredDescriber) DescribeMetadata(metadata metav1.ObjectMeta) {
 	d.Describe("metadata", metadataInfo)
 }
 
-// JsonEncode encodes d.output to json
-func (d *StructuredDescriber) JsonEncode() string {
+// JSONEncode encodes d.output to json
+func (d *StructuredDescriber) JSONEncode() string {
 	byteBuffer := &bytes.Buffer{}
 	encoder := json.NewEncoder(byteBuffer)
 	encoder.SetEscapeHTML(false)