Cannot read property 'getAuthInstance' of undefined
<html>
<head>
<meta name="google-signin-client_id" content="YOUR_CLIENT_ID">
</head>
<body>
<script>
function signOut() {
var auth2 = gapi.auth2.getAuthInstance();
auth2.signOut().then(function () {
console.log('User signed out.');
});
}
function onLoad() {
gapi.load('auth2', function() {
gapi.auth2.init();
});
}
</script>
<a href="#" onclick="signOut();">Sign out</a>
<script src="https://apis.google.com/js/platform.js?onload=onLoad" async defer></script>
</body>
</html>