why not using async since the entire code base using it? Promise is used in few places due to SDK dependency.

can you show me how you want the code to be written? async keyword is needed when we have await in the function; and wrapping the entire function as a Promise

it is already returning promise which means you are using asynchronous or blocking code in the function. async functions use an implicit Promise to return results anyway. Keeping code consistent would be good.

my point is we do not add async unnecessary and it is not encourage. it is not about consistency.
Sorry I do not get your point on why you want to add async?

I can write the function in the manner but not simply adding an async keyword.

export const getSubscriptions = async (
  rc: IRequestContext
): Promise<ISubscriptionItem[]> => {
  logger.info("attempting to get subscription list");
  const creds = await loginWithServicePrincipalSecret(
    rc.servicePrincipalId!,
    rc.servicePrincipalPassword!,
    rc.servicePrincipalTenantId!
  );
  const client = new SubscriptionClient(creds);
  const subsciptions = await client.subscriptions.list();
  const result = (subsciptions || []).map(s => {
    return {
      id: s.subscriptionId!,
      name: s.displayName!
    };
  });
  logger.info("Successfully acquired subscription list");
  return result;
};