develop a regisry with kubernetes headless service

[gsmini]

I am very honored to use go-micro and to be involved in this project.
when i study go-micro v4 and deploy it with k8s , i found the registry plugin kubernets plugin, it inspired me.

i found the kubernets plugin use client.go to call apiServer which make it not very friendly to use. Coincidentally, I've been studying kubenetes recently, and i found when the Service.ClusterIP is None we can take the Service as a DNS server, so i
try to make this happen in registry.

apiVersion: v1
kind: Service
metadata:
  name: user-svc
  namespace: default
spec:
  clusterIP: None #attention here
  ports:
    - port: 8080
  selector:
    app:  user

  sessionAffinity: ClientIP
  sessionAffinityConfig:
    clientIP:
        timeoutSeconds: 3600

so, this kubernetes-headless-svc is to resolve Service name to get the endpoints ip which are also podIP u call.

root@hecs-410147:~# kubectl get endpoints
NAME                  ENDPOINTS             AGE
frontend-svc          10.32.0.4:8080       100s
user-svc              10.32.0.9:8080        200s

the plugin return 10.32.0.9:8080 to fronted applition to call

it is so easy finish this work ,just use a net package like this:

package main
import (
	"fmt"
	"net"
)

func main() {
	//we just use net.LookupIP to get ip address of www.twitter.com
	ipRecords, err := net.LookupIP("www.twitter.com")
	if err != nil {
		panic(err)
	}
	for _, value := range ipRecords {
		fmt.Println(value.String())
	}
}

you can take a look of README.md to get the detail document about it , and i give a example to use this plugin in examples folder.

[Davincible]

Thanks a lot for your PR! Interesting approach!

Could you please have a look at the lining issues, and translate all Chinese to English?

Then I can review the PR in more detail.

[gsmini]

Thanks a lot for your PR! Interesting approach!

Could you please have a look at the lining issues, and translate all Chinese to English?

Then I can review the PR in more detail.

I'm sorry that it took me so long to get your message, because I was delayed by some things. According to your requirements and the error prompt in test.sh, I made relevant modifications and changed the Chinese commnets in the code into English. Please kindly help to approve this pr again.
Look forward to your reply, I am always online!

[gsmini]

this repo is for demo how to use this plugin :https://github.com/orgs/go-micro-v4-demo/repositories
the "frontend" service call " user " and "helloword" service, especially in frontend/main.go showed the whole code :

const UserSvcName = "user-svc"        //the name of k8s service the micoservice "user"  used 
const HelloWordSvcName = "helloworld" //the name of k8s service the micoservice "helloworld" used
func main() {
        // u can use this plugin so easily like this
	UserSvc := &k8sHeadlessSvc.Service{Namespace: "default", SvcName: UserSvcName, PodPort: 8080}
	//HelloWordSvc := &k8sHeadlessSvc.Service{Namespace: "default", SvcName: HelloWordSvcName, PodPort: 9090}
	reg := k8sHeadlessSvc.NewRegistry([]*k8sHeadlessSvc.Service{UserSvc})
	srv := micro.NewService(
		micro.Server(mhttp.NewServer()), 
		micro.Client(mgrpc.NewClient())) 
	srv.Init(
		micro.Name(service),
		micro.Version(version),
		micro.Address("0.0.0.0:8080"), 
		micro.Registry(reg),
	)
       .....

[gsmini]

@Davincible When you have time, you can help me with the code review thanks .