code: func NewTimer(o Observer) *Timer {
  	return &Timer{
  		begin:    time.Now(),
  		observer: o,
  	}
  }
docs: // NewTimer creates a new Timer. The provided Observer is used to observe a
  // duration in seconds. Timer is usually used to time a function call in the
  // following way:
  //    func TimeMe() {
  //        timer := NewTimer(myHistogram)
  //        defer timer.ObserveDuration()
  //        // Do actual work.
  //    }