/// <reference types="node" />
import { IncomingHttpHeaders } from "http";
/**
 * Returns the value of the requested header in a case insensitive way.
 *
 * @param {Object} headers The headers object.
 * @param {string} headerName The name of the header we need.
 * @returns string | undefined
 */
export default function getHeaderValue(headers: IncomingHttpHeaders, headerName: string): string | string[] | undefined;