My async/await function is not waiting in AWS Lambda. What am I missing?

Question

I have a function in AWS Lambda to retrieve user details in Stripe. But the code after the function is executing first. What am I missing?

In my case, the function calls a Stripe function that returns a customer object.

I think the details of the Stripe function are not relevant for this specific question--the issue is the structure of my async/await:

module.exports.getUserName = async (event, context)=>{

  [code to get customerId from stripe]

  var customerName

  await stripe.customers.retrieve(customerId, function(err, customer){
      if (err){}
      else{
       customerName = customer.name
     }
  })

  console.log('This should run after stripe.customers.retrieve')

}

Right now the console.log statement runs first. I've also tried wrapping the Stripe function in a separate async function, and also tried adding try/catch. But it's not working yet.

How can I be sure that the console log statement instead runs after stripe.customers.retrieve ?

Answer 1

Edit: I checked the source for the npm stripe package. All the functions do return Promises, but if you additionally supply a callback, they're scheduled to be called on the next event loop (immediately after your console.log runs).

All you need to do is simply don't provide a callback if you'll be using the promise. Use Promise.then() instead:

await stripe.customers.retrieve(customerId).then(customer => {
   customerName = customer.name
   resolve()
}).catch(_=>{})

---

Old answer (still works, but very redundant):

await is to be used with Promises, it doesn't magically convert asynchronous code to synchronous. I can see from the old-fashioned function(err, customer){ callback that your stripe.customers.retrieve() function does not return a Promise, so the await won't actually do anything.

You need to wrap it in a promise in order to use with async/await:

await new Promise((resolve,reject) => { 
   stripe.customers.retrieve(customerId, function(err, customer) {
      if(!err) {
         customerName = customer.name
         resolve()
      }
   })
})