Setting Cookie No Longer Working After Deploy

After deploying both my backend written in Go (using railway) and frontend written using React (using Vercel) setting cookies no longer seems to work. This wasn’t a problem when working with both of them locally, only after I deployed them.

For context, here is what sets the cookie:

    http.SetCookie(w, &http.Cookie{
        Name:     "auth_token",
        Value:    tokenString,
        Expires:  expirationTime,
        Secure: true,
        SameSite: http.SameSiteLaxMode,
        HttpOnly: true,
        Domain:  domainName,
    })

This is the request I am making on the frontend:

      const res = await axios.post(api.login, formData, {
        withCredentials: true, 
      });

I’m expecting the cookie to be set in the frontend like it was when I was testing and working locally, however after deploying both frontend and backend it seems to not work.