code/viewer_request/index.js
const HEADER_NAME = 'x-original-host';
exports.handler = (event, _, callback) => {
const request = event.Records[0].cf.request;
const host = request.headers['host'][0].value;
request.headers[HEADER_NAME] = [
{
key: HEADER_NAME,
value: host,
},
];
callback(null, request);
};