Chore: parallel checking dead domains

Build/lib/get-runner-geoip.ts

@@ -0,0 +1,30 @@
+import { $$fetch } from './fetch-retry';
+
+export interface RunnerGeoIP {
+  ip: string,
+  country: string,
+  region: string,
+  city: string,
+  asn: number,
+  asOrg: string,
+  longitude: number,
+  latitude: number,
+  timezone: string,
+  cfEdgeIP: string
+}
+
+/**
+ * Fetch the current machine's egress IP and geo info. Used to confirm that
+ * each matrix shard landed on a different GitHub-hosted runner region / egress
+ * IP — the premise that lets sharding spread DoH load and dodge rate limits.
+ *
+ * Returns `null` on any failure so it never aborts the actual domain check.
+ */
+export async function getRunnerGeoIP(): Promise<RunnerGeoIP | null> {
+  try {
+    const res = await $$fetch('https://ip.api.skk.moe/cf-geoip');
+    return await res.json() as RunnerGeoIP;
+  } catch {
+    return null;
+  }
+}