Avoid async/await for run()

lib/server.js

@@ -15,7 +15,6 @@ const serve = fn => server((req, res) => {
 
 module.exports = exports = serve
 
-exports.run = run
 exports.json = json
 exports.send = send
 exports.sendError = sendError
@@ -39,6 +38,22 @@ async function run(req, res, fn) {
   }
 }
 
+exports.run = (req, res, fn) => {
+  fn(req, res).then(val => {
+    // Return 204 No Content if value is null
+    if (val === null) {
+      send(res, 204, null)
+    }
+
+    // Return a undefined-null value -> send
+    if (undefined !== val) {
+      send(res, res.statusCode || 200, val)
+    }
+  }).catch(err => {
+    sendError(req, res, err)
+  })
+}
+
 // maps requests to buffered raw bodies so that
 // multiple calls to `json` work as expected
 const rawBodyMap = new WeakMap()