根据建立cloudflare Worker服务的指示新建一个Cloudflare Worker。
具体代码如下：

// Website you intended to retrieve for users.
const upstream = 'api.openai.com'

// Custom pathname for the upstream website.
const upstream_path = '/'

// Website you intended to retrieve for users using mobile devices.
const upstream_mobile = upstream

// Countries and regions where you wish to suspend your service.
const blocked_region = []

// IP addresses which you wish to block from using your service.
const blocked_ip_address = ['0.0.0.0', '127.0.0.1']

// Whether to use HTTPS protocol for upstream address.
const https = true

// Whether to disable cache.
const disable_cache = false

// Replace texts.
const replace_dict = {
  '$upstream': '$custom_domain',
}

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

async function fetchAndApply(request) {
  const region = request.headers.get('cf-ipcountry').toUpperCase();
  const ip_address = request.headers.get('cf-connecting-ip');
  const user_agent = request.headers.get('user-agent');

  let response = null;
  let url = new URL(request.url);
  let url_hostname = url.hostname;

  if (https == true) {
    url.protocol = 'https:';
  } else {
    url.protocol = 'http:';
  }

  if (await device_status(user_agent)) {
    var upstream_domain = upstream;
  } else {
    var upstream_domain = upstream_mobile;
  }

  url.host = upstream_domain;
  if (url.pathname == '/') {
    url.pathname = upstream_path;
  } else {
    url.pathname = upstream_path + url.pathname;
  }

  if (blocked_region.includes(region)) {
    response = new Response('Access denied: WorkersProxy is not available in your region yet.', {
      status: 403
    });
  } else if (blocked_ip_address.includes(ip_address)) {
    response = new Response('Access denied: Your IP address is blocked by WorkersProxy.', {
      status: 403
    });
  } else {
    let method = request.method;
    let request_headers = request.headers;
    let new_request_headers = new Headers(request_headers);

    new_request_headers.set('Host', upstream_domain);
    new_request_headers.set('Referer', url.protocol + '//' + url_hostname);

    let original_response = await fetch(url.href, {
      method: method,
      headers: new_request_headers,
      body: request.body
    })

    connection_upgrade = new_request_headers.get("Upgrade");
    if (connection_upgrade && connection_upgrade.toLowerCase() == "websocket") {
      return original_response;
    }

    let original_response_clone = original_response.clone();
    let original_text = null;
    let response_headers = original_response.headers;
    let new_response_headers = new Headers(response_headers);
    let status = original_response.status;

    if (disable_cache) {
      new_response_headers.set('Cache-Control', 'no-store');
    }

    new_response_headers.set('access-control-allow-origin', '*');
                             new_response_headers.set('access-control-allow-credentials', true);
                             new_response_headers.delete('content-security-policy');
                             new_response_headers.delete('content-security-policy-report-only');
                             new_response_headers.delete('clear-site-data');

                             if (new_response_headers.get("x-pjax-url")) {
                             new_response_headers.set("x-pjax-url", response_headers.get("x-pjax-url").replace("//" + upstream_domain, "//" + url_hostname));
                             }

                             const content_type = new_response_headers.get('content-type');
                             if (content_type != null && content_type.includes('text/html') && content_type.includes('UTF-8')) {
                             original_text = await replace_response_text(original_response_clone, upstream_domain, url_hostname);
                             } else {
                             original_text = original_response_clone.body
                             }

                             response = new Response(original_text, {
                             status,
                             headers: new_response_headers
                             })
                             }
                             return response;
                             }

                             async function replace_response_text(response, upstream_domain, host_name) {
                             let text = await response.text()

                             var i, j;
                             for (i in replace_dict) {
                             j = replace_dict[i]
                             if (i == '$upstream') {
                             i = upstream_domain
                             } else if (i == '$custom_domain') {
                             i = host_name
                             }

                             if (j == '$upstream') {
                             j = upstream_domain
                             } else if (j == '$custom_domain') {
                             j = host_name
                             }

                             let re = new RegExp(i, 'g')
                             text = text.replace(re, j);
                             }
                             return text;
                             }


                             async function device_status(user_agent_info) {
                             var agents = ["Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod"];
                             var flag = true;
                             for (var v = 0; v < agents.length; v++) {
                             if (user_agent_info.indexOf(agents[v]) > 0) {
                             flag = false;
                             break;
                             }
                             }
                             return flag;
                             }