Merge pull request #224 from iamqizhao/master

refactor service registration code a bit.

server.go

@@ -139,17 +139,20 @@ func NewServer(opt ...ServerOption) *Server {
 // server. Called from the IDL generated code. This must be called before
 // invoking Serve.
 func (s *Server) RegisterService(sd *ServiceDesc, ss interface{}) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	// Does some sanity checks.
-	if _, ok := s.m[sd.ServiceName]; ok {
-		grpclog.Fatalf("grpc: Server.RegisterService found duplicate service registration for %q", sd.ServiceName)
-	}
 	ht := reflect.TypeOf(sd.HandlerType).Elem()
 	st := reflect.TypeOf(ss)
 	if !st.Implements(ht) {
 		grpclog.Fatalf("grpc: Server.RegisterService found the handler of type %v that does not satisfy %v", st, ht)
 	}
+	s.register(sd, ss)
+}
+
+func (s *Server) register(sd *ServiceDesc, ss interface{}) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if _, ok := s.m[sd.ServiceName]; ok {
+		grpclog.Fatalf("grpc: Server.RegisterService found duplicate service registration for %q", sd.ServiceName)
+	}
 	srv := &service{
 		server: ss,
 		md:     make(map[string]*MethodDesc),