add handler recorder

limiter/rate/limiter.go

@@ -1,6 +1,7 @@
 package rate
 
 import (
+	"errors"
 	"sort"
 	"time"
 
@@ -8,6 +9,10 @@ import (
 	"golang.org/x/time/rate"
 )
 
+var (
+	ErrRateLimit = errors.New("rate limit")
+)
+
 type rlimiter struct {
 	limiter *rate.Limiter
 }