Fix unit tests and comments

Signed-off-by: z1cheng <imchench@gmail.com>

cmd/plugin/commands/certs/certs.go

@@ -18,6 +18,7 @@ package certs
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/spf13/cobra"
 
@@ -47,7 +48,8 @@ func CreateCommand(flags *genericclioptions.ConfigFlags) *cobra.Command {
 
 	cmd.Flags().String("host", "", "Get the cert for this hostname")
 	if err := cobra.MarkFlagRequired(cmd.Flags(), "host"); err != nil {
-		fmt.Printf("error marking flag as required: %v", err)
+		util.PrintError(err)
+		os.Exit(1)
 	}
 	pod = util.AddPodFlag(cmd)
 	deployment = util.AddDeploymentFlag(cmd)

cmd/plugin/kubectl/kubectl.go

@@ -78,9 +78,7 @@ func execToWriter(args []string, writer io.Writer) error {
 	}
 
 	go func() {
-		if _, err := io.Copy(writer, op); err != nil {
-			fmt.Printf("Error copying output: %v\n", err)
-		}
+		io.Copy(writer, op) //nolint:errcheck
 	}()
 	err = cmd.Run()
 	if err != nil {