Feature: Thread-safe database reloading

[a1ekas]

Hi folks.

Thank you very much for your work on the library.
The current implementation is already very useful and the ability to safely reload the database will make it even more convenient.

It would be cool if you could add support for thread-safe reloading of the binary database, so that when you update a file on disk you can pick up the new version without disrupting the running goroutines.

What might this look like?

• A goroutine is running in the background, which keeps track of the base file (for example, by date of change).
• If the file is updated, we call some Reload function, but in such a way that the current requests continue to work without errors.
• The new database data is loaded and replaced in the library used as safely as possible.

It is important that nothing crashes during the update. Goroutines reading data should not stumble upon closed files or invalid structures.