code: func LogOnPanic(id int64, err interface{}, stacktrace []string, _ *http.Request) {
  	logMutex.Lock()
  	defer logMutex.Unlock()
  
  	log.Printf("panic=%016x message=%v\n", id, err)
  	for _, line := range stacktrace {
  		log.Printf("panic=%016x %s", id, line)
  	}
  }
docs: // LogOnPanic logs the given panic and its stacktrace, prefixing each line with
  // the panic ID.