code: func QueryRange(url, query, start, end string, step time.Duration, p printer) int {
  	config := api.Config{
  		Address: url,
  	}
  
  	// Create new client.
  	c, err := api.NewClient(config)
  	if err != nil {
  		fmt.Fprintln(os.Stderr, "error creating API client:", err)
  		return 1
  	}
  
  	var stime, etime time.Time
  
  	if end == "" {
  		etime = time.Now()
  	} else {
  		etime, err = parseTime(end)
  		if err != nil {
  			fmt.Fprintln(os.Stderr, "error parsing end time:", err)
  			return 1
  		}
  	}
  
  	if start == "" {
  		stime = etime.Add(-5 * time.Minute)
  	} else {
  		stime, err = parseTime(start)
  		if err != nil {
  			fmt.Fprintln(os.Stderr, "error parsing start time:", err)
  		}
  	}
  
  	if !stime.Before(etime) {
  		fmt.Fprintln(os.Stderr, "start time is not before end time")
  	}
  
  	if step == 0 {
  		resolution := math.Max(math.Floor(etime.Sub(stime).Seconds()/250), 1)
  		// Convert seconds to nanoseconds such that time.Duration parses correctly.
  		step = time.Duration(resolution) * time.Second
  	}
  
  	// Run query against client.
  	api := v1.NewAPI(c)
  	r := v1.Range{Start: stime, End: etime, Step: step}
  	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
  	val, err := api.QueryRange(ctx, query, r)
  	cancel()
  
  	if err != nil {
  		fmt.Fprintln(os.Stderr, "query error:", err)
  		return 1
  	}
  
  	p.printValue(val)
  	return 0
  }
docs: // QueryRange performs a range query against a Prometheus server.