code: func (t *trace) LazyPrintf(format string, a ...interface{}) {
  	newfmt, newvals := addTrace(t, format, a...)
  	Log.Printf(newfmt, newvals...)
  	t.trace.LazyPrintf(format, a...)
  }
docs: // LazyPrintf evaluates its arguments with fmt.Sprintf each time the
  // /debug/requests page is rendered. Any memory referenced by a will be
  // pinned until the trace is finished and later discarded.