AWS Lambda Node.js 8.10 + API Gateway

responseをreturnで返すと動いた。

const aws = require('aws-sdk');
var response = {
    statusCode: 200,
    body: JSON.stringify('Hello from Lambda!')
};

exports.handler = async (event) => {
    // TODO implement
    let ddb_ = new aws.DynamoDB.DocumentClient({region: 'ap-northeast-1'});
    try
    {
        var res_ = await ddb_.scan({TableName : 'テーブル名'}).promise();
        response["body"] = JSON.stringify(res_);
    }
    catch(err)
    {
        response["body"] = JSON.stringify(err);
    }
    return response;
};