npm install @google-cloud/channel

// Reads the secrets from a `oauth2.keys.json` file, which should be downloaded// from the Google Developers Console and saved in the same directory with the// sample app.// This sample app only calls read-only methods from the Channel API. Include// additional scopes if calling methods that modify the configuration.const SCOPES = ['https://www.googleapis.com/auth/apps.order'];async function listCustomers(authClient, accountNumber) {  // Imports the Google Cloud client library  const {CloudChannelServiceClient} = require('@google-cloud/channel');  // Instantiates a client using OAuth2 credentials.  const sslCreds = grpc.credentials.createSsl();  const credentials = grpc.credentials.combineChannelCredentials(    sslCreds,    grpc.credentials.createFromGoogleCredential(authClient)  );  // Instantiates a client  const client = newCloudChannelServiceClient({    sslCreds: credentials,  });  // Calls listCustomers() method  const customers = await client.listCustomers({    parent: `accounts/${accountNumber}`,  });  console.info(customers);}/** * Create a new OAuth2Client, and go through the OAuth2 content * workflow.  Return the full client to the callback. */function getAuthenticatedClient(keys) {  return new Promise((resolve, reject) => {    // Create an oAuth client to authorize the API call. Secrets are kept in a    // `keys.json` file, which should be downloaded from the Google Developers    // Console.    const oAuth2Client = new OAuth2Client(      keys.web.client_id,      keys.web.client_secret,      // The first redirect URL from the `oauth2.keys.json` file will be used      // to generate the OAuth2 callback URL. Update the line below or edit      // the redirect URL in the Google Developers Console if needed.      // This sample app expects the callback URL to be      // 'http://localhost:3000/oauth2callback'      keys.web.redirect_uris[0]    );    // Generate the url that will be used for the consent dialog.    const authorizeUrl = oAuth2Client.generateAuthUrl({      access_type: 'offline',      scope: SCOPES.join(' '),    });    // Open an http server to accept the oauth callback. In this example, the    // only request to our webserver is to /oauth2callback?code=<code>    const server = http      .createServer(async (req, res) => {        try {          if (req.url.indexOf('/oauth2callback') > -1) {            // Acquire the code from the querystring, and close the web            // server.            const qs = new url.URL(req.url, 'http://localhost:3000')              .searchParams;            const code = qs.get('code');            console.log(`Code is ${code}`);            res.end('Authentication successful! Please return to the console.');            server.destroy();            // Now that we have the code, use that to acquire tokens.            const r = await oAuth2Client.getToken(code);            // Make sure to set the credentials on the OAuth2 client.            oAuth2Client.setCredentials(r.tokens);            console.info('Tokens acquired.');            resolve(oAuth2Client);          }        } catch (e) {          reject(e);        }      })      .listen(3000, () => {        // Open the browser to the authorize url to start the workflow.        // This line will not work if you are running the code in the        // environment where a browser is not available. In this case,        // copy the URL and open it manually in a browser.        console.info(`Opening the browser with URL: ${authorizeUrl}`);        open(authorizeUrl, {wait: false}).then(cp => cp.unref());      });    destroyer(server);  });}async function main(accountNumber, keys) {  // TODO: uncomment with your account number  // const accountNumber = '1234'  // TODO: uncomment this line with your oAuth2 file  //const keys = require('./oauth2.keys.json');  getAuthenticatedClient(keys).then(authClient =>    listCustomers(authClient, accountNumber)  );}