chrome.runtime.onSuspend.addListener not firing

Question

I am having a chrome extension connected to native messaging application. I need to do some cleanup when the chrome extension suspends. I am trying to use chrome.runtime.onSuspend.addListener but it is not working. Here is my code : -

Manifest.json

"background": {"scripts": ["background.js"], 
               "persistent": false},   

background.js

    function Connect() {
        console.log("Connected");

        ext = chrome.runtime.connectNative('foxtrot');   
        chrome.runtime.onSuspend.addListener(function () {
            ext.postMessage({ message: "clean and close" });   
        });
    }