rewrite timeout feature for node <10

Author: sw-yx

Diff for: lib/serve.js

@@ -136,19 +136,26 @@ function createHandler(dir, static, timeout) {
       callback
     );
 
-    var invocationTimeoutRef = null
-    
+    var invocationTimeoutRef = null;
+
     Promise.race([
       promiseCallback(promise, callback),
       new Promise(function(resolve) {
         invocationTimeoutRef = setTimeout(function() {
-          handleInvocationTimeout(response, timeout)
-          resolve()
-        }, timeout * 1000)
+          handleInvocationTimeout(response, timeout);
+          resolve();
+        }, timeout * 1000);
       })
-    ]).finally(() => {
-      clearTimeout(invocationTimeoutRef)
-    })
+    ]).then(
+      result => {
+        clearTimeout(invocationTimeoutRef);
+        return result; // not used, but writing this to avoid future footguns
+      },
+      err => {
+        clearTimeout(invocationTimeoutRef);
+        throw err;
+      }
+    );
   };
 }