Fix whois-ns-fallback request once again (#143)

try-catch in getNameservers() doesn't work as expected because
a promise is returned succesfully before it's evaluation and
try-catch in the function won't catch if it fails later on.

lib/index.js

@@ -364,9 +364,11 @@ export default class Now extends EventEmitter {
     });
   }
 
-  getNameservers (domain, { fallback = false } = {}) {
-    try {
-      return this.retry(async (bail, attempt) => {
+  getNameservers (domain) {
+    return new Promise((resolve, reject) => {
+      let fallback = false;
+
+      this.retry(async (bail, attempt) => {
         if (this._debug) console.time(`> [debug] #${attempt} GET /whois-ns${fallback ? '-fallback' : ''}`);
         const res = await this._fetch(`/whois-ns${fallback ? '-fallback' : ''}?domain=${encodeURIComponent(domain)}`);
         if (this._debug) console.timeEnd(`> [debug] #${attempt} GET /whois-ns${fallback ? '-fallback' : ''}`);
@@ -375,18 +377,17 @@ export default class Now extends EventEmitter {
           if ((!body.nameservers || body.nameservers.length === 0) && !fallback) {
             // if the nameservers are `null` it's likely
             // that our whois service failed to parse it
-            return this.getNameservers(domain, { fallback: true });
+            fallback = true;
+            throw new Error('Invalid whois response');
           }
 
           return body;
         } else {
+        if (attempt > 1) fallback = true;
           throw new Error(`Whois error (${res.status}): ${body.error.message}`);
         }
-      });
-    } catch (err) {
-      if (fallback) throw err;
-      return this.getNameservers(domain, { fallback: true });
-    }
+      }).then((body) => resolve(body));
+    });
   }
 
   // _ensures_ the domain is setup (idempotent)