chore: add timeout mechanism for fetch calls (#3649)

packages/netlify-cms-lib-util/src/unsentRequest.js

@@ -3,6 +3,27 @@ import curry from 'lodash/curry';
 import flow from 'lodash/flow';
 import isString from 'lodash/isString';
 
+let controller;
+let signal;
+if (typeof window !== 'undefined') {
+  controller = window.AbortController && new AbortController();
+  signal = controller && controller.signal;
+}
+
+const timeout = 60;
+const fetchWithTimeout = (input, init) => {
+  if (controller && signal && !init.signal) {
+    setTimeout(() => controller.abort(), timeout * 1000);
+    return fetch(input, { ...init, signal }).catch(e => {
+      if (e.name === 'AbortError') {
+        throw new Error(`Request timed out after ${timeout} seconds`);
+      }
+      throw e;
+    });
+  }
+  return fetch(input, init);
+};
+
 const decodeParams = paramsString =>
   List(paramsString.split('&'))
     .map(s => List(s.split('=')).map(decodeURIComponent))
@@ -51,7 +72,7 @@ const ensureRequestArg2 = func => (arg, req) => func(arg, maybeRequestArg(req));
 // This actually performs the built request object
 const performRequest = ensureRequestArg(req => {
   const args = toFetchArguments(req);
-  return fetch(...args);
+  return fetchWithTimeout(...args);
 });
 
 // Each of the following functions takes options and returns another
@@ -91,4 +112,5 @@ export default {
   withParams,
   withRoot,
   withNoCache,
+  fetchWithTimeout,
 };