use dep as denpendency managment tool

vendor/golang.org/x/time/rate/rate_go17.go

@@ -0,0 +1,21 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.7
+
+package rate
+
+import "context"
+
+// Wait is shorthand for WaitN(ctx, 1).
+func (lim *Limiter) Wait(ctx context.Context) (err error) {
+	return lim.waitN(ctx, 1)
+}
+
+// WaitN blocks until lim permits n events to happen.
+// It returns an error if n exceeds the Limiter's burst size, the Context is
+// canceled, or the expected wait time exceeds the Context's Deadline.
+func (lim *Limiter) WaitN(ctx context.Context, n int) (err error) {
+	return lim.waitN(ctx, n)
+}