title: Unable to get message contents of email using google API
body: <p>I'm trying to write some code in order to retrieve an email message using Google APIs. I followed the documentation provided here: <a href="https://developers.google.com/gmail/api/reference/rest/v1/users.messages/get?apix_params=%7B%22userId%22%3A%22prashanthpillay2%40gmail.com%22%2C%22id%22%3A%22176d95971a2ffce1%22%7D" rel="nofollow noreferrer">https://developers.google.com/gmail/api/reference/rest/v1/users.messages/get?apix_params=%7B%22userId%22%3A%22prashanthpillay2%40gmail.com%22%2C%22id%22%3A%22176d95971a2ffce1%22%7D</a>, to implement my showMessageContent function and used the quickstart sample found here: <a href="https://developers.google.com/gmail/api/quickstart/nodejs?authuser=1" rel="nofollow noreferrer">https://developers.google.com/gmail/api/quickstart/nodejs?authuser=1</a>, but when I execute the code I only get the message ID displayed and nothing about the actual message. Any help would be great, I'm pretty new to this stuff.</p>
  <p>Entire Code for my index.js file:</p>
  <pre><code>const fs = require('fs');
  const readline = require('readline');
  const {google} = require('googleapis');
  let messageArr = [];
  
  // If modifying these scopes, delete token.json.
  const SCOPES = ['https://www.googleapis.com/auth/gmail.readonly'];
  // The file token.json stores the user's access and refresh tokens, and is
  // created automatically when the authorization flow completes for the first
  // time.
  const TOKEN_PATH = 'token.json';
  
  // Load client secrets from a local file.
  fs.readFile('client_secret.json', (err, content) =&gt; {
    if (err) return console.log('Error loading client secret file:', err);
    // Authorize a client with credentials, then call the Gmail API.
    authorize(JSON.parse(content), listMessages);
  });
  
  /**
   * Create an OAuth2 client with the given credentials, and then execute the
   * given callback function.
   * @param {Object} credentials The authorization client credentials.
   * @param {function} callback The callback to call with the authorized client.
   */
  function authorize(credentials, callback) {
    const {client_secret, client_id, redirect_uris} = credentials.installed;
    const oAuth2Client = new google.auth.OAuth2(
        client_id, client_secret, redirect_uris[0]);
  
    // Check if we have previously stored a token.
    fs.readFile(TOKEN_PATH, (err, token) =&gt; {
      if (err) return getNewToken(oAuth2Client, callback);
      oAuth2Client.setCredentials(JSON.parse(token));
      callback(oAuth2Client);
    });
  }
  
  /**
   * Get and store new token after prompting for user authorization, and then
   * execute the given callback with the authorized OAuth2 client.
   * @param {google.auth.OAuth2} oAuth2Client The OAuth2 client to get token for.
   * @param {getEventsCallback} callback The callback for the authorized client.
   */
  function getNewToken(oAuth2Client, callback) {
    const authUrl = oAuth2Client.generateAuthUrl({
      access_type: 'offline',
      scope: SCOPES,
    });
    console.log('Authorize this app by visiting this url:', authUrl);
    const rl = readline.createInterface({
      input: process.stdin,
      output: process.stdout,
    });
    rl.question('Enter the code from that page here: ', (code) =&gt; {
      rl.close();
      oAuth2Client.getToken(code, (err, token) =&gt; {
        if (err) return console.error('Error retrieving access token', err);
        oAuth2Client.setCredentials(token);
        // Store the token to disk for later program executions
        fs.writeFile(TOKEN_PATH, JSON.stringify(token), (err) =&gt; {
          if (err) return console.error(err);
          console.log('Token stored to', TOKEN_PATH);
        });
        callback(oAuth2Client);
      });
    });
  }
  
  async function listMessages(auth) {
    const gmail = google.gmail({version: 'v1', auth});
    gmail.users.messages.list({
      userId: 'me',
      maxResults: 1
    }, (err, res) =&gt; {
      if (err) return console.log('The API returned an error: ' + err);
      const messages = res.data.messages;
      if (messages) {
        console.log('Messages:');
        let i=0;
        messages.forEach((message) =&gt; {
            messageArr[i] = message.id;
            console.log(messageArr[i]);
            i++;
        
        });
      } else {
        console.log('No messages found.');
      }
  
      
    }); 
    
    setTimeout(() =&gt; 
    {console.log(gmail.users.messages.get(
      {
        userId: 'me',
        id: '176daac2fedbf7f9'
      }, (err, res) =&gt; {
        if (err) return console.log('The API returned an error: ' + err);
        else{
          return res;
        }
        
      })
    );
  
    
  
    }, 3000);
  </code></pre>
  <p>}</p>
  <p>Problem function:</p>
  <pre><code>    async function listMessages(auth) {
    const gmail = google.gmail({version: 'v1', auth});
    gmail.users.messages.list({
      userId: 'me',
      maxResults: 1
    }, (err, res) =&gt; {
      if (err) return console.log('The API returned an error: ' + err);
      const messages = res.data.messages;
      if (messages) {
        console.log('Messages:');
        let i=0;
        messages.forEach((message) =&gt; {
            messageArr[i] = message.id;
            console.log(messageArr[i]);
            i++;
        
        });
      } else {
        console.log('No messages found.');
      }
  
      
    }); 
    
    setTimeout(() =&gt; 
    {console.log(gmail.users.messages.get(
      {
        userId: 'me',
        id: '176daac2fedbf7f9'
      }, (err, res) =&gt; {
        if (err) return console.log('The API returned an error: ' + err);
        else{
          return res;
        }
        
      })
    );
  
    
  
    }, 3000);
  
  }
  </code></pre>
  <p>The result when I run it is in the attached picture</p>
  <p><a href="https://i.stack.imgur.com/T5g1u.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T5g1u.png" alt="Command Prompt Execution" /></a></p>
  <p>When the callback in setTimeout runs, it results in the result being undefined, which doesn't make sense to me since I passed the the correct ID manually to <code>gmail.users.messages.get()</code>.</p>