code: func (f *FST) IsMatchWithVal(addr int) (bool, uint64) {
  	s, err := f.decoder.stateAt(addr, nil)
  	if err != nil {
  		return false, 0
  	}
  	return s.Final(), s.FinalOutput()
  }
docs: // IsMatchWithVal returns if this state is a matching state in this Automaton
  // and also returns the final output value for this state