code: func (t *trace) Finish() {
  	if t.err {
  		incrError(t)
  	}
  	incr(t)
  	duration(t)
  	if t.err {
  		incrError(t)
  	}
  	t.trace.Finish()
  }
docs: // Finish declares that this trace is complete.
  // The trace should not be used after calling this method.