From 5f4412996d93e7ce45c955b4ba731707034f73d2 Mon Sep 17 00:00:00 2001
From: Gyu-Ho Lee <gyuhox@gmail.com>
Date: Mon, 27 Feb 2017 17:07:13 -0800
Subject: [PATCH] clientv3: define error type for closed watcher

---
 clientv3/naming/grpc.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/clientv3/naming/grpc.go b/clientv3/naming/grpc.go
index fa7a2aa3f..9bb92ea61 100644
--- a/clientv3/naming/grpc.go
+++ b/clientv3/naming/grpc.go
@@ -16,6 +16,7 @@ package naming
 
 import (
 	"encoding/json"
+	"fmt"
 
 	etcd "github.com/coreos/etcd/clientv3"
 	"golang.org/x/net/context"
@@ -25,6 +26,8 @@ import (
 	"google.golang.org/grpc/naming"
 )
 
+var ErrWatcherClosed = fmt.Errorf("naming: watch closed")
+
 // GRPCResolver creates a grpc.Watcher for a target to track its resolution changes.
 type GRPCResolver struct {
 	// Client is an initialized etcd client.
@@ -77,7 +80,7 @@ func (gw *gRPCWatcher) Next() ([]*naming.Update, error) {
 	// process new events on target/*
 	wr, ok := <-gw.wch
 	if !ok {
-		gw.err = grpc.Errorf(codes.Unavailable, "naming: watch closed")
+		gw.err = grpc.Errorf(codes.Unavailable, "%s", ErrWatcherClosed)
 		return nil, gw.err
 	}
 	if gw.err = wr.Err(); gw.err != nil {