/** Create a refreshable value. Define `load` function and use correct `refreshPeriodMillis` interval. */
const currentAccessToken = new AsyncFreshValue({
        refreshPeriodMillis: 0,
        load: async (settings) => {
            const response = await fetchAccessToken(/*....*/);
            settings.refreshPeriodMillis = Date.now() - response.expirationTime;
            return response.token;
        }
    });

// Use the fresh value :

async function getA(): A {
    const accessToken: string = await currentAccessToken.get();
    return fetch(accessToken, /** A-call params.*/);
}

async function getB(): B {
    const accessToken: string = await currentAccessToken.get();
    return fetch(accessToken, /** B-call params.*/);
}