This code, I have written at least 3 times, now, I don't want to forget it anymore.

kubernetes-client-go-exec.go

package main

import (
	"os"

	"k8s.io/api/core/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/kubernetes/scheme"
	"k8s.io/client-go/tools/clientcmd"
	"k8s.io/client-go/tools/remotecommand"
)

func main() {

	config, err := clientcmd.BuildConfigFromFlags("", os.Getenv("HOME")+"/.kube/config")

	if err != nil {
		panic(err)
	}

	client, err := kubernetes.NewForConfig(config)

	req := client.CoreV1().RESTClient().Post().
		Resource("pods").
		Name("cp-launcher-vault-696c6c8f79-fqmkq").
		Namespace("default").
		SubResource("exec").
		Param("container", "vault").
		VersionedParams(&v1.PodExecOptions{
			Container: "vault",
			Command:   []string{"cat", "/vault/config/config.json"},
			Stdin:     false,
			Stdout:    true,
			Stderr:    true,
			TTY:       false,
		}, scheme.ParameterCodec)

	exec, err := remotecommand.NewSPDYExecutor(config, "POST", req.URL())
	if err != nil {
		panic(err)
	}

	err = exec.Stream(remotecommand.StreamOptions{Stdout: os.Stdout, Stderr: os.Stderr, Tty: false})
	if err != nil {
		panic(err)
	}
}