New creates and returns a new LevelDB(file-based) storage instance based on the "directoryPath".

NewFromDB same as `New` but accepts an already-created custom leveldb connection instead.

Options used to open the leveldb database, defaults to leveldb's default values.

ReadOptions used to iterate over the database, defaults to leveldb's default values.

WriteOptions used to put and delete, defaults to leveldb's default values.

Database the LevelDB(file-based) session storage.