S3.getObject "Converting circular structure to JSON" error in node 8.10

const AWS = require('aws-sdk');
const s3 = new AWS.S3();

exports.handler = async (event) => {
    // TODO implement
    
    var params = {
        Bucket: 'bucketName',
        Key: `Key`
    };

    return s3.getObject(params, function(err, data) {
        if (err) { // an error occurred
        console.log(err)
            return 'Hello from Lambda!, error';
        } else { // successful response
            console.log(data);
            return 'Hello from Lambda! data';
        }
    });
    
};

{
  "errorMessage": "Converting circular structure to JSON",
  "errorType": "TypeError",
  "stackTrace": []
}

START RequestId: f66642cd-6561-11e8-9101-45144114db6b Version: $LATEST
Unable to stringify response body as json: Converting circular structure to JSON: TypeError
    at JSON.stringify (<anonymous>)
2018-06-01T06:06:46.750Z	f66642cd-6561-11e8-9101-45144114db6b	{ AcceptRanges: 'bytes',
  LastModified: 2018-05-13T08:32:08.000Z,
  ContentLength: 198,
  ETag: '"6c437a16c722e7f90b76dc3198355248"',
  ContentType: 'application/json',
  Metadata: {},
  Body: <Buffer 7b 0a 20 20 20 20 22 6d 61 6b 65 22 3a 20 22 46 69 61 74 22 2c 0a 20 20 20 20 22 6d 6f 64 65 6c 22 3a 20 22 35 30 30 22 2c 0a 20 20 20 20 22 72 72 70 ... > }
END RequestId: f66642cd-6561-11e8-9101-45144114db6b
REPORT RequestId: f66642cd-6561-11e8-9101-45144114db6b	Duration: 936.36 ms	Billed Duration: 1000 ms 	Memory Size: 128 MB	Max Memory Used: 32 MB	

[SamWSoftware]

I had to promisify the .getObject to make it work with async

[srchase]

@taylor-zr

The ‘response’ you’re attempting to return is the actual request, which has a circular reference to itself, resulting in the error you’re seeing.

Could you try this instead?

exports.handler = async (event) => {
    return await s3.getObject(params).promise()
    .then((res) => {
        return res.Body.toString('utf-8');
    })
    .catch((err) => {
        return err;
    });
};