Add Limiter interface

options.go

@@ -14,6 +14,17 @@ import (
 	"github.com/go-redis/redis/internal/pool"
 )
 
+// Limiter is the interface of a rate limiter or a circuit breaker.
+type Limiter interface {
+	// Allow returns a nil if operation is allowed or an error otherwise.
+	// If operation is allowed client must report the result of operation
+	// whether is a success or a failure.
+	Allow() error
+	// ReportResult reports the result of previously allowed operation.
+	// nil indicates a success, non-nil error indicates a failure.
+	ReportResult(result error)
+}
+
 type Options struct {
 	// The network type, either tcp or unix.
 	// Default is tcp.