Ec2 Instance Data Not pushed in array - node.js

Question

I want to query all ec2 across regions.
I can log the data, but I can't push it to an array.
Here is the example
to loop over regions
let AWS = require('aws-sdk');
function regionConfig(reg) {
return new AWS.EC2({
region: reg
});
}
to list the allowed regions
const listRegions = async () => {
ec2 = regionConfig('eu-west-1')
let regionsArray = []
return await new Promise((resolve, reject) => {
ec2.describeRegions({}, function(err, data) {
if (err) reject(err, err.stack); // an error occurred
else {
for (let region of data.Regions) {
regionsArray.push(region.RegionName)
}
resolve(regionsArray)
}
});
})
}
to describe the ec2 instances
const describeIntances = async () => {
regions = await listRegions()
let instances = [];
return await new Promise((resolve, reject) => {
for(let i of regions) {
let ec2 = regionConfig(i)
ec2.describeInstances({}, function(err, data) {
if (err) reject(err, err.stack); // an error occurred
else {
let instances = [];
console.log(data)
for (let reservation of data.Reservations) {
instances.push(reservation)
}
resolve(instances)
}
})
}
})
}
execute the lambda
const handler = async (event) => {
const regions = await listRegions()
// console.log(regions)
const describeInstances = await describeIntances()
console.log(describeInstances)
const response = {
statusCode: 200,
body: JSON.stringify('Hello from Lambda!'),
};
return response;
};
handler()
I can see data for as many instances as I have, but when I push, the array is empty
could it be because of the async?