Update go dependencies

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

@@ -6,12 +6,11 @@
 package rate
 
 import (
+	"context"
 	"fmt"
 	"math"
 	"sync"
 	"time"
-
-	"golang.org/x/net/context"
 )
 
 // Limit defines the maximum frequency of some events.
@@ -244,8 +243,12 @@ func (lim *Limiter) WaitN(ctx context.Context, n int) (err error) {
 	if !r.ok {
 		return fmt.Errorf("rate: Wait(n=%d) would exceed context deadline", n)
 	}
-	// Wait
-	t := time.NewTimer(r.DelayFrom(now))
+	// Wait if necessary
+	delay := r.DelayFrom(now)
+	if delay == 0 {
+		return nil
+	}
+	t := time.NewTimer(delay)
 	defer t.Stop()
 	select {
 	case <-t.C: