test/index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        async function addCache() {
            try {
                const cache = await caches.open("test"); 
                await cache.add("index.html")
                await cache.add("https://api.github.com", {
                    method: "GET"
                })

                console.log(`added`)
            }
            catch(ex) {
                console.log(`error ${ex}`)
            }
            finally {
                console.log("Finally done.")
            }
            

        }

          

        async function getCache() {
            try {
                const cache = await caches.open("test"); 
                const res = await cache.match("https://api.github.com")
                const json = await res.json();
                console.log(json)
            }
            catch(ex) {
                console.log(`error ${ex}`)
            }
            finally {
                console.log("Finally done.")
            }

        }
    </script>
    
</body>
</html>