implement k8s service discovery (#988)

* implement k8s service discovery

* simplify code

* use default namespace if not provided

* disable codecov bot comment

* ignore adhoc dir

* simplify building target in NewClient

* reformat code

* Fix filepath (#990)

* format code, and reorg imports (#991)

* add more unit test

Co-authored-by: anqiansong <anqiansong@gmail.com>

zrpc/config.go

@@ -23,7 +23,8 @@ type (
 	// A RpcClientConf is a rpc client config.
 	RpcClientConf struct {
 		Etcd      discov.EtcdConf `json:",optional"`
-		Endpoints []string        `json:",optional=!Etcd"`
+		Endpoints []string        `json:",optional"`
+		Target    string          `json:",optional"`
 		App       string          `json:",optional"`
 		Token     string          `json:",optional"`
 		Timeout   int64           `json:",default=2000"`