onMessage.js

// This will wait for the astilectron namespace to be ready
document.addEventListener('astilectron-ready', function() {
    // This will listen to messages sent by GO
    astilectron.onMessage(function(message) {
        // Process message
        if (message.name === "event.name") {
            return {payload: message.message + " world"};
        }
    });
})