code: func (*HandlerT) MutexProfile(file string, nsec uint) error {
  	runtime.SetMutexProfileFraction(1)
  	time.Sleep(time.Duration(nsec) * time.Second)
  	defer runtime.SetMutexProfileFraction(0)
  	return writeProfile("mutex", file)
  }
docs: // MutexProfile turns on mutex profiling for nsec seconds and writes profile data to file.
  // It uses a profile rate of 1 for most accurate information. If a different rate is
  // desired, set the rate and write the profile manually.