fix comment.

Signed-off-by: imxyb <xyb4638@gmail.com>

cluster/loadbalance/consistent_hash.go

@@ -26,7 +26,9 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+)
 
+import (
 	"github.com/apache/dubbo-go/cluster"
 	"github.com/apache/dubbo-go/common/constant"
 	"github.com/apache/dubbo-go/common/extension"
@@ -39,8 +41,10 @@ const (
 	HashArguments  = "hash.arguments"
 )
 
-var selectors = make(map[string]*ConsistentHashSelector)
-var re = regexp.MustCompile(constant.COMMA_SPLIT_PATTERN)
+var (
+	selectors = make(map[string]*ConsistentHashSelector)
+	re        = regexp.MustCompile(constant.COMMA_SPLIT_PATTERN)
+)
 
 func init() {
 	extension.SetLoadbalance(ConsistentHash, NewConsistentHash)
@@ -99,10 +103,6 @@ type ConsistentHashSelector struct {
 
 func NewConsistentHashSelector(invokers []protocol.Invoker, methodName string,
 	hashCode uint32) *ConsistentHashSelector {
-	if len(invokers) == 0 {
-		panic("none of invokers")
-	}
-
 	selector := &ConsistentHashSelector{}
 	selector.virtualInvokers = make(map[uint32]protocol.Invoker)
 	selector.hashCode = hashCode