code: func SamplingPercent(p int) TracerOption {
  	if p < 0 || p > 100 {
  		panic("sampling rate must be between 0 and 100")
  	}
  	return func(o *tracerOptions) *tracerOptions {
  		o.samplingPercent = p
  		return o
  	}
  }
docs: // SamplingPercent sets the tracing sampling rate as a percentage value.
  // It panics if p is less than 0 or more than 100.
  // SamplingPercent and MaxSamplingRate are mutually exclusive.