You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.go
    path of file: ./repos/learning/golang/practice/go-crontab/source/prepare/etcd_usage/demo6
    
    the code of the file until where you have to start completion: package main

import (
	"github.com/coreos/etcd/clientv3"
	"time"
	"fmt"
	"context"
)

func main() {
	var (
		config clientv3.Config
		client *clientv3.Client
		err error
		lease clientv3.Lease
		leaseGrantResp *clientv3.LeaseGrantResponse
		leaseId clientv3.LeaseID
		putResp *clientv3.PutResponse
		getResp *clientv3.GetResponse
		keepResp *clientv3.LeaseKeepAliveResponse
		keepRespChan <-chan *clientv3.LeaseKeepAliveResponse
		kv clientv3.KV
	)

	config = clientv3.Config{
		Endpoints: []string{"36.111.184.221:2379"}, // 集群列表
		DialTimeout: 5 * time.Second,
	}

	// 建立一个客户端
	if client, err = clientv3.New(config); err != nil {
		fmt.Println(err)
		return
	}

	// 申请一个lease（租约）
	lease = clientv3.NewLease(client)

	// 申请一个10秒的租约
	if leaseGrantResp, err = lease.Grant(context.TODO(), 10); err != nil {
		fmt.Println(err)
		return
	}

	// 拿到租约的ID
	leaseId = leaseGrantResp.ID

	// 5秒后会取消自动续租
	if keepRespChan, err =
    
func main() {
	var (
		config clientv3.Config
		client *clientv3.Client
		err error
		lease clientv3.Lease
		leaseGrantResp *clientv3.LeaseGrantResponse
		leaseId clientv3.LeaseID
		putResp *clientv3.PutResponse
		getResp *clientv3.GetResponse
		keepResp *clientv3.LeaseKeepAliveResponse
		keepRespChan <-chan *clientv3.LeaseKeepAliveResponse
		kv clientv3.KV
	)

	config = clientv3.Config{
		Endpoints: []string{"36.111.184.221:2379"}, // 集群列表
		DialTimeout: 5 * time.Second,
	}

	// 建立一个客户端
	if client, err = clientv3.New(config); err != nil {
		fmt.Println(err)
		return
	}

	// 申请一个lease（租约）
	lease = clientv3.NewLease(client)

	// 申请一个10秒的租约
	if leaseGrantResp, err = lease.Grant(context.TODO(), 10); err != nil {
		fmt.Println(err)
		return
	}

	// 拿到租约的ID
	leaseId = leaseGrantResp.ID

	// 5秒后会取消自动续租
	if keepRespChan, err = lease.KeepAlive(context.TODO(), leaseId); err != nil {
		fmt.Println(err)
		return
	}

	// 处理续约应答的协程
	go func() {
		for {
			select {
			case keepResp = <- keepRespChan:
				if keepRespChan == nil {
					fmt.Println("租约已经失效了")
					goto END
				} else {	// 每秒会续租一次, 所以就会受到一次应答
					fmt.Println("收到自动续租应答:", keepResp.ID)
				}
			}
		}
		END:
	}()

	// 获得kv API子集
	kv = clientv3.NewKV(client)

	// Put一个KV, 让它与租约关联起来, 从而实现10秒后自动过期
	if putResp, err = kv.Put(context.TODO(), "/cron/lock/job1", "", clientv3.WithLease(leaseId)); err != nil {
		fmt.Println(err)
		return
	}

	fmt.Println("写入成功:", putResp.Header.Revision)

	// 定时的看一下key过期了没有
	for {
		if getResp, err = kv.Get(context.TODO(), "/cron/lock/job1"); err != nil {
			fmt.Println(err)
			return
		}
		if getResp.Count == 0 {
			fmt.Println("kv过期了")
			break
		}
		fmt.Println("还没过期:", getResp.Kvs)
		time.Sleep(2 * time.Second)
	}
}