parseHeaders = (rawHeaders) => {
  const parsed = {};
  let key;
  let val;
  let i;
  rawHeaders && rawHeaders.split("\n").forEach(function parser(line) {
    i = line.indexOf(":");
    key = line.substring(0, i).trim().toLowerCase();
    val = line.substring(i + 1).trim();
    if (!key || parsed[key] && ignoreDuplicateOf[key]) {
      return;
    }
    if (key === "set-cookie") {
      if (parsed[key]) {
        parsed[key].push(val);
      } else {
        parsed[key] = [val];
      }
    } else {
      parsed[key] = parsed[key] ? parsed[key] + ", " + val : val;
    }
  });
  return parsed;
}
A timeout in milliseconds to abort a request. If set to 0 (default) a
timeout is not created.