The following simple codes got: Error executing Gatsby Function. It works fine on my local environment. Could you anyone point if there are simple errors? Thanks!

import { GatsbyFunctionRequest, GatsbyFunctionResponse } from "gatsby"

export default async function handler(
    req: GatsbyFunctionRequest,
    res: GatsbyFunctionResponse
): Promise<void> {
res.json(req.headers)
return Promise.resolve()
}