code: func (db *DB) HSet(key []byte, field []byte, value []byte) (int64, error) {
  	if err := checkHashKFSize(key, field); err != nil {
  		return 0, err
  	} else if err := checkValueSize(value); err != nil {
  		return 0, err
  	}
  
  	t := db.hashBatch
  	t.Lock()
  	defer t.Unlock()
  
  	n, err := db.hSetItem(key, field, value)
  	if err != nil {
  		return 0, err
  	}
  
  	err = t.Commit()
  	return n, err
  }
docs: // HSet sets the field with value of key.