code: func MeasureSince(key []string, start time.Time) {
  	normalizeKeys(key)
  
  	GetMetrics().MeasureSince(key, start)
  }
docs: // MeasureSince creates a timing metric that records
  // the duration of elapsed time since `start`
  // Usage:
  //     MeasureSince([]string{"my","namespace","action"}, time.Now())
  // Frequently used in a defer:
  //    defer MeasureSince([]string{"my","namespace","action"}, time.Now())