minor codestyle fixes, turn async/await in metricsApp into a conventional promise

Makefile

@@ -3,8 +3,8 @@
 test:
 	npm test
 lint:
-	node_modules/eslint/bin/eslint.js src
-	node_modules/.bin/dtslint types
+	npx eslint src
+	npm run dtslint-next
 coverage:
 	node_modules/istanbul/lib/cli.js cover \
 		-i 'src/*' \

spec/index.spec.js

@@ -206,7 +206,7 @@ describe('index', () => {
       bypass: (req)=> {
         // metrics added here to attempt skipping /metrics
         // this should fail though, because serving /metrics preceeds bypassing
-        return !!req.url.match(/test|bad.word|metrics/)
+        return !!req.url.match(/test|bad.word|metrics/);
       }
     });
     app.use(instance);

src/index.js

@@ -206,9 +206,10 @@ function main(opts) {
   };
 
   if (opts.metricsApp) {
-    opts.metricsApp.get(opts.metricsPath || '/metrics', async (req, res, next) => {
+    opts.metricsApp.get(opts.metricsPath || '/metrics', (req, res) => {
       res.set('Content-Type', opts.promRegistry.contentType);
-      return res.end(await opts.promRegistry.metrics());
+      opts.promRegistry.metrics()
+        .then(metrics => res.end(metrics));
     });
   }