Remove the use of grpc-go's Metadata field

We also revoke the deprecation of the Metadata field, Users
can store whatever information related to each endpoint. We
just don't need to pass the value to grpc-go's Metadata.

Signed-off-by: Benjamin Wang <benjamin.ahrtr@gmail.com>

Author: ahrtr

clientv3/naming/endpoints/endpoints.go

@@ -29,8 +29,7 @@ type Endpoint struct {
 	// Since etcd 3.1
 	Addr string
 
-	// Metadata is the information associated with Addr, which may be used
-	// to make load balancing decision.
+	// Metadata is the information associated with Addr.
 	// Since etcd 3.1
 	Metadata interface{}
 }

clientv3/naming/resolver/resolver.go

@@ -110,8 +110,7 @@ func convertToGRPCAddress(ups map[string]*endpoints.Update) []gresolver.Address
 	var addrs []gresolver.Address
 	for _, up := range ups {
 		addr := gresolver.Address{
-			Addr:     up.Endpoint.Addr,
-			Metadata: up.Endpoint.Metadata,
+			Addr: up.Endpoint.Addr,
 		}
 		addrs = append(addrs, addr)
 	}