addEventListener('fetch', event => {
    event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
    const response = await fetch(request)
    // 添加新的頭
    response.headers.append("X-Hello", "hello from ctyun")
    // 修改舊的頭
    response.headers.set("Etag" ,"4kf36KRuEB")
    return response
}