fix: ensure background work is finished when response has 3xx or 5xx status code

Author: pieh

src/run/handlers/server.ts

@@ -100,7 +100,7 @@ export default async (request: Request) => {
 
     // Contrary to the docs, this resolves when the headers are available, not when the stream closes.
     // See https://github.com/fastly/http-compute-js/blob/main/src/http-compute-js/http-server.ts#L168-L173
-    const response = await toComputeResponse(resProxy)
+    let response = await toComputeResponse(resProxy)
 
     if (requestContext.responseCacheKey) {
       span.setAttribute('responseCacheKey', requestContext.responseCacheKey)
@@ -121,7 +121,7 @@ export default async (request: Request) => {
     // TODO: Remove once a fix has been rolled out.
     if ((response.status > 300 && response.status < 400) || response.status >= 500) {
       const body = await response.text()
-      return new Response(body || null, response)
+      response = new Response(body || null, response)
     }
 
     const keepOpenUntilNextFullyRendered = new TransformStream({