Client-go throws error of "GroupVersion is required when initializing a RESTClient"

[OnurAkkose]

Even I set the config it wanted , it keep to throws the same error. In this code I try to copy a file from inside of a pod to local.

package main

import (
	"bytes"
	"fmt"
	"log"
	"path/filepath"

	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/runtime/serializer"
	"k8s.io/cli-runtime/pkg/genericclioptions"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/kubernetes/scheme"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/util/homedir"
	"k8s.io/kubectl/pkg/cmd/cp"
	"k8s.io/kubectl/pkg/cmd/util"
)

const GroupName = "api"

var SchemeGroupVersion = schema.GroupVersion{Group: GroupName, Version: "v1"}

func main() {
	var kubeConfig string

	if home := homedir.HomeDir(); home != "" {
		kubeConfig = filepath.Join(home, ".kube", "config")
	}

	config, err := clientcmd.BuildConfigFromFlags("", kubeConfig)
	config.GroupVersion = &SchemeGroupVersion
	if err != nil {
		fmt.Println(err)
	}
	clientset, err := kubernetes.NewForConfig(config)
	if err != nil {
		panic(err)
	}

	config.NegotiatedSerializer = serializer.WithoutConversionCodecFactory{CodecFactory: scheme.Codecs}

	podexec := NewPodExec(*config, clientset)
	err = podexec.copyFile()
	if err != nil {
		panic(err)
	}

}

type PodExec struct {
	RestConfig *rest.Config
	ClientSet  *kubernetes.Clientset
}

func NewPodExec(config rest.Config, clientset *kubernetes.Clientset) *PodExec {
	return &PodExec{
		RestConfig: &config,
		ClientSet:  clientset,
	}

}

func (p *PodExec) CopyFileFromThePod(sourceFilePath string, destinationFilePath string, containername, namespace string) (*bytes.Buffer, *bytes.Buffer, *bytes.Buffer, error) {
	ioStreams, in, out, errOut := genericclioptions.NewTestIOStreams()
	copyOptions := cp.NewCopyOptions(ioStreams)
	copyOptions.Clientset = p.ClientSet
	copyOptions.ClientConfig = p.RestConfig
	copyOptions.Container = containername
	var copt genericclioptions.RESTClientGetter = &genericclioptions.ConfigFlags{}

	nf := util.NewFactory(copt)
	cobra := cp.NewCmdCp(nf, ioStreams)
	sourceFilePath = namespace + "/" + containername + ":" + sourceFilePath
	cobra.Run(cobra, []string{sourceFilePath, destinationFilePath})

	err := cobra.Execute()
	if err != nil {
		log.Fatal(err)
	}
	return in, out, errOut, nil
}

func (podexec *PodExec) copyFile() error {
	podExec := NewPodExec(*podexec.RestConfig, podexec.ClientSet)
	_, out, _, err := podExec.CopyFileFromThePod("/var/lib/test.db", "/test/test.db", "test-app-sec-deployment-8f769fb8b-dpl9z", "default")
	if err != nil {
		fmt.Printf("%v\n", err)
		return err
	}
	fmt.Println("out:")
	fmt.Printf("%s", out.String())
	return nil
}