code: func MatchAbHandler(key string, value interface{}, a, b LogHandler) LogHandler {
  	return FuncHandler(func(r *Record) error {
  		if r.Context[key] == value {
  			return a.Log(r)
  		} else if b != nil {
  			return b.Log(r)
  		}
  
  		return nil
  	})
  }
docs: // If match then A handler is called otherwise B handler is called