Update serve.js to clear the timeout if a function invocation is a su…

…ccess within the timeout.

lib/serve.js

@@ -135,12 +135,20 @@ function createHandler(dir, static, timeout) {
       { clientContext: buildClientContext(request.headers) || {} },
       callback
     );
+
+    var invocationTimeoutRef = null
+
     Promise.race([
       promiseCallback(promise, callback),
-      setTimeout(function() {
-        handleInvocationTimeout(response, timeout)
-      }, timeout * 1000)
-    ])
+      new Promise(function(resolve) {
+        invocationTimeoutRef = setTimeout(function() {
+          handleInvocationTimeout(response, timeout)
+          resolve()
+        }, timeout * 1000)
+      })
+    ]).finally(() => {
+      clearTimeout(invocationTimeoutRef)
+    })
   };
 }