fix: omit some fetch options when running in Cloudflare Workers env

closes #255

README.md

@@ -139,6 +139,7 @@ Legend:
 | -- | -- | -- |
 | Node.js | LTS ^12.19.0 || ^14.15.0 | |
 | Electron | ^12.0.0 | see <sup>[1]</sup> |
+| Cloudflare Workers | ✓ | see <sup>[2], [4]</sup> |
 | Deno | experimental | see Deno's [Web Cryptography API roadmap](https://github.com/denoland/deno/issues/11690) |
 | React Native | ✕ | has no available and usable crypto runtime |
 | IE | ✕ | implements old version of the Web Cryptography API specification |

src/runtime/browser/fetch_jwks.ts

@@ -12,10 +12,17 @@ const fetchJwks: FetchFunction = async (url: URL, timeout: number) => {
  const response = await globalThis.fetch(url.href, {
  signal: controller ? controller.signal : undefined,
  redirect: 'manual',
- referrerPolicy: 'no-referrer',
- credentials: 'omit',
- mode: 'cors',
  method: 'GET',
+ // do not pass referrerPolicy, credentials, and mode when running
+ // in Cloudflare Workers environment
+ // @ts-expect-error
+ ...(typeof globalThis.WebSocketPair === 'undefined'
+ ? {
+ referrerPolicy: 'no-referrer',
+ credentials: 'omit',
+ mode: 'cors',
+ }
+ : undefined),
  })
 
  if (response.status !== 200) {