_metcd/server.go
func GRPCServer(s Server, options ...grpc.ServerOption) *grpc.Server {
	srv := grpc.NewServer(options...)
	//etcdserverpb.RegisterAuthServer(srv, s)
	//etcdserverpb.RegisterClusterServer(srv, s)
	etcdserverpb.RegisterKVServer(srv, s)
	//etcdserverpb.RegisterLeaseServer(srv, s)
	//etcdserverpb.RegisterMaintenanceServer(srv, s)
	//etcdserverpb.RegisterWatchServer(srv, s)
	return srv
}
func GRPCServer(s Server, options ...grpc.ServerOption) *grpc.Server {
	srv := grpc.NewServer(options...)
	//etcdserverpb.RegisterAuthServer(srv, s)
	//etcdserverpb.RegisterClusterServer(srv, s)
	etcdserverpb.RegisterKVServer(srv, s)
	//etcdserverpb.RegisterLeaseServer(srv, s)
	//etcdserverpb.RegisterMaintenanceServer(srv, s)
	//etcdserverpb.RegisterWatchServer(srv, s)
	return srv
}
// GRPCServer converts a metcd.Server to a *grpc.Server.