asyncExample.js

const AWS = require('aws-sdk');

const client = new AWS.SecretsManager({});

// Call the AWS API and return a Promise
function getAwsSecret(secretName) {
  return client.getSecretValue({ SecretId: secretName }).promise();
}

// Create a async function to use the Promise
// Top level await is a proposal
async function getAwsSecretAsync (secretName) {
  var error;
  var response = await getAwsSecret(secretName).catch(err => (error = err));
  return [error, response];
}

// Call the async function and return NodeJS callback style
module.exports = function asyncExample () {
  var [error, secret] = getAwsSecretAsync('dev/MySecret/MyService');
  
  if (error) {
    // Trigger an error and halt
    console.error(error);
    return;
  }
  
  // Use the result
  console.debug(secret);
}

Top level async/await is now available in Node.js LTS (v16.15.0 as of now).