How can I add the session token to every API call called from both server and client components?

I currently have Auth.js set up and working and what I am trying to do is to create a function in my API class that adds the session token to the authorization header of the request. I managed to get it to work but my issue is that it only works for server components (due to the method of Auth.js for getting the session). I need it to work both when the API is called from a server as well as a client component. When I try to call it from a client component it gives an error.

This is the code I have on my API class:

import { SessionUserType } from '@/types/auth.types';
import { auth } from '../lib/auth';

class ApiService {

    // Set Request Token

    private async setRequestToken() {
        const session = await auth();
        const user = session?.user as SessionUserType;
        let token = user?.access_token ? `Bearer ${user?.access_token}` : '';

        return token;
    }

    // Get Method

    async get(url: string) {
        const response = await fetch(url, {
            headers: {
                'Authorization': await this.setRequestToken()
            }
        });

        return this.handleResponse(response);
    }
}

The auth method comes from the auth provider I set up following the Auth.js docs:

import NextAuth from "next-auth"
import Credentials from "next-auth/providers/credentials"

import AuthService from "@/services/auth.service"
 
export const { handlers, signIn, signOut, auth } = NextAuth({
  providers: [
    Credentials({
        credentials: {
          email: {},
          password: {},
        },
        authorize: async (credentials) => {
          let data = {
            email: credentials.email as string,
            password: credentials.password as string,
          }
  
          try {
            const user = await AuthService.login(data);
            return user;
          } catch(error: any) {
            throw new Error(error?.message || error);
          }          
        },
    }),
  ],
})

What would be the way to setup the API class function so that it can get the session token when used both from server and client components?

Thanks in advance.

I managed to solve it like this:

import { auth } from '../lib/auth';
import { getSession } from "next-auth/react";

private async setRequestToken() {
    let userSession;

    if (typeof window == "undefined") {
        userSession = await auth();
    } else { 
        userSession = await getSession();
    }
        
    const user = userSession?.user as SessionUserType;
    const token = user?.access_token;

    return token;
}

The typeof window will be undefined when the request is made from a server component so with this condition the request will use the server or client method of Auth.js to get the user session.