refactor: simplify cluster refresh

cluster.go

@@ -140,66 +140,53 @@ func (c *clusterClient) refresh() (err error) {
 type clusterslots struct {
 	reply RedisResult
 	addr  string
+	ver   int
+}
+
+func (s clusterslots) parse(tls bool) map[string]group {
+	if s.ver < 7 {
+		return parseSlots(s.reply.val, s.addr)
+	}
+	return parseShards(s.reply.val, s.addr, tls)
+}
+
+func getClusterSlots(c conn) clusterslots {
+	if c.Version() < 7 {
+		return clusterslots{reply: c.Do(context.Background(), cmds.SlotCmd), addr: c.Addr(), ver: c.Version()}
+	}
+	return clusterslots{reply: c.Do(context.Background(), cmds.ShardsCmd), addr: c.Addr(), ver: c.Version()}
 }
 
 func (c *clusterClient) _refresh() (err error) {
-	type versionedResult struct {
-		version int
-		reply   RedisResult
-		addr    string
-	}
-	var (
-		reply   RedisMessage
-		addr    string
-		version int
-	)
 	c.mu.RLock()
-	results := make(chan versionedResult, len(c.conns))
+	results := make(chan clusterslots, len(c.conns))
 	pending := make([]conn, 0, len(c.conns))
 	for _, cc := range c.conns {
 		pending = append(pending, cc)
 	}
 	c.mu.RUnlock()
 
+	var result clusterslots
 	for i := 0; i < cap(results); i++ {
 		if i&3 == 0 { // batch CLUSTER SLOTS/CLUSTER SHARDS for every 4 connections
 			for j := i; j < i+4 && j < len(pending); j++ {
 				go func(c conn) {
-					var reply RedisResult
-					if c.Version() < 7 {
-						reply = c.Do(context.Background(), cmds.SlotCmd)
-					} else {
-						reply = c.Do(context.Background(), cmds.ShardsCmd)
-					}
-					results <- versionedResult{
-						version: c.Version(),
-						reply:   reply,
-						addr:    c.Addr(),
-					}
+					results <- getClusterSlots(c)
 				}(pending[j])
 			}
 		}
-		r := <-results
-		version = r.version
-		addr = r.addr
-		reply, err = r.reply.ToMessage()
-		if len(reply.values) != 0 {
+		result = <-results
+		err = result.reply.Error()
+		if len(result.reply.val.values) != 0 {
 			break
 		}
 	}
-	pending = nil
-
 	if err != nil {
 		return err
 	}
+	pending = nil
 
-	var groups map[string]group
-	if version < 7 {
-		groups = parseSlots(reply, addr)
-	} else {
-		groups = parseShards(reply, addr, c.opt.TLSConfig != nil)
-	}
-
+	groups := result.parse(c.opt.TLSConfig != nil)
 	conns := make(map[string]conn, len(groups))
 	for _, g := range groups {
 		for _, addr := range g.nodes {