build: implement services image build and CI release. (#2920)

* build: implement services image build.

* remove unused tools

* update test.

* update images.

* update dockerfile and go mod.

* update go mod.

* Add comments.

* update go pkg.

* update loadConfig and discovery logic in kubernetes.

* update go pkg and discovery field.

* update Load method args.

config/discovery.yml

@@ -5,6 +5,9 @@ etcd:
   username: ''
   password: ''
 
+kubernetes:
+  namespace: default
+
 rpcService:
   user: user-rpc-service
   friend: friend-rpc-service
@@ -14,6 +17,4 @@ rpcService:
   group: group-rpc-service
   auth: auth-rpc-service
   conversation: conversation-rpc-service
-  third: third-rpc-service
-
-
+  third: third-rpc-service