code: func (p *Params) BonusThreshold(v float64) *Params {
  	if v >= 0 {
  		p.bonusThreshold = v
  	}
  	return p
  }
docs: // BonusThreshold overrides the default value for the minimum similarity score
  // for which Match() can assign a bonus.
  // The new value must be zero or positive. Note that a threshold greater than 1
  // effectively makes Match() become the equivalent of Similarity().