code: func RunDuration(b *pb.Build) (duration time.Duration, ok bool) {
  	start, startErr := ptypes.Timestamp(b.StartTime)
  	end, endErr := ptypes.Timestamp(b.EndTime)
  	if startErr != nil || start.IsZero() || endErr != nil || end.IsZero() {
  		return 0, false
  	}
  
  	return end.Sub(start), true
  }
docs: // RunDuration returns duration between build start and end.