code: func (s *Client) includeStat(rate float32) bool {
  	if s == nil {
  		return false
  	}
  
  	// test for nil in case someone builds their own
  	// client without calling new (result is nil sampler)
  	if s.sampler != nil {
  		return s.sampler(rate)
  	}
  	return DefaultSampler(rate)
  }
docs: // check for nil client, and perform sampling calculation