New shutdown script for cross-platform ease of use; implement host option in config file; minor code cleanup.

shutdown.mjs

@@ -0,0 +1,21 @@
+import { readFile, writeFile, unlink } from 'node:fs/promises';
+
+const config = Object.freeze(JSON.parse(await readFile(new URL("./src/config.json", import.meta.url))));
+
+const serverUrl = (base => {
+  try {
+    base = new URL(config.host);
+  } catch (e) {
+    base = new URL("http://a");
+    base.host = config.host;
+  }
+  base.port = process.env.PORT || config.port;
+  return Object.freeze(base);
+})();
+
+const shutdown = new URL("./src/.shutdown", import.meta.url);
+
+await writeFile(shutdown, "");
+try {await fetch(new URL("/test-shutdown", serverUrl))}
+catch (e) {await unlink(shutdown)}
+process.exitCode = 0;