code: func (c *CrossRequestRetryDelay) BeforeSign(r *request.Request) {
  	now := time.Now()
  	delay := c.backoff.ComputeDelayForRequest(now)
  	if delay > 0 {
  		glog.Warningf("Inserting delay before AWS request (%s) to avoid RequestLimitExceeded: %s",
  			describeRequest(r), delay.String())
  		r.Config.SleepDelay(delay)
  
  		// Avoid clock skew problems
  		r.Time = now
  	}
  }
docs: // BeforeSign is added to the Sign chain; called before each request