licensing – How can I use my personal code at work

We are starting a project at work and I found out that a library I wrote outside of work could be very beneficial.

I asked if I could bring my code with protection at the same time. My only interest is to use this code in the future without any restrictions.

At first, I would simply open-source it and the problem is solved but the company may be against that. It is understandable because the library will get bigger and improved when used in work and that is done by company hours/money.

Can someone suggest what I can do? Is open-source without “publishing” make sense or is there a specific license I should look into?