error-lambda-proxy.js

module.exports.hello = (event, context, callback) => {
  const errorResponse = {
    statusCode: 400,
    headers: {
      "x-custom-header" : "my custom header value"
    },
    body: JSON.stringify({
      message: 'Bad request Dude',
    }),
  };

  // Do not use callback(new error(errorResponse)) in lambda-proxy
  // error response
  callback(null, errorResponse);
};