By default gorm uses the type `varbinary(255)` for []byte in database models. 255 characters isn't enough for a plugin config therefore we use longblob instead.
we use the database connection inside the handlers from the http
framework, therefore concurrent access occurs. Sqlite cannot handle
concurrent writes, so we limit sqlite to one connection.
see https://github.com/mattn/go-sqlite3/issues/274
饺子w