How to use `getSession()` on NextJS Server action ?

I'm working with 2 services: a Next.js frontend and a Hono backend. I have the database and Better Auth configured on the Hono backend. Authentication works perfectly on the frontend client side using getSession() from the auth client. However, when I try to authenticate users in server actions (/api routes), getSession() doesn't work.
Could someone please help me with this issue?