auth-token.js

function authorize_api_usage(client_id, scope, user) {
  return new Promise((res,rej) => {
    const token_client = google.accounts.oauth2.initTokenClient({
      client_id,
      scope,
      hint: user.email,
      callback: (response) => {
        if (!response.access_token) {
          return rej('authorization-failed');
        }
        res();
      }
    });
    token_client.requestAccessToken({prompt: ''});
  });
}