code: func makeDynsampleKey(ev *event.Event, options GlobalOptions) string {
  	key := make([]string, len(options.DynSample))
  	for i, field := range options.DynSample {
  		if val, ok := ev.Data[field]; ok {
  			switch val := val.(type) {
  			case bool:
  				key[i] = strconv.FormatBool(val)
  			case int64:
  				key[i] = strconv.FormatInt(val, 10)
  			case float64:
  
  				key[i] = strconv.FormatFloat(val, 'E', -1, 64)
  			case string:
  				key[i] = val
  			default:
  				key[i] = "" // skip it
  			}
  		}
  	}
  	return strings.Join(key, "_")
  }
docs: // makeDynsampleKey pulls in all the values necessary from the event to create a
  // key for dynamic sampling