【高优先级】在discovery模块中实现Etcd服务发现逻辑

[iSuperCoder]

可参考arana-db中的etcd服务发现逻辑：
https://github.com/arana-db/arana/blob/master/pkg/registry/etcd/discovery.go

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You can refer to the etcd service discovery logic in arana-db:
https://github.com/arana-db/arana/blob/master/pkg/registry/etcd/discovery.go

[yizhibian]

I want to try #578, pls assign to me

[yizhibian]

@iSuperCoder 抱歉之前因为有些事耽搁了这个任务，我在做这个任务的时候遇到了一个问题想和老师请教一下。
我看了seata用etcd做服务注册中心的源码，为什么seata将服务信息注册到etcd时其格式是registry-seata-CLUSTER_NAME-ADDRESS而不是registry-seata-CLUSTER_NAME呢？为什么需要通过服务本身的地址作为key的一部分呢？

如果我理解有误，希望老师指出，谢谢！

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@iSuperCoder Sorry for delaying this task because of some things. I encountered a problem when doing this task and would like to ask the teacher for advice.
I read the source code of seata using etcd as a service registry. Why does seata register service information in etcd in the format registry-seata-CLUSTER_NAME-ADDRESS instead of registry-seata-CLUSTER_NAME? Why do you need to use the address of the service itself as part of the key?

If I understand something wrong, I hope the teacher will point it out, thank you!