fetch not working

async chat(message) {
    console.log(message);
    let payload = {
        method: "POST",
        headers: {
            "Content-Type": "application/json",
            "Authorization": "Bearer " + TWITCH_APP_TOKEN,
            "Client-Id": TWITCH_APP_ID
        },
        body: {
            "broadcaster_user_id": "12341234",
            "sender_id": "12341234",
            "message": message,
            "for_source_only": "true"
        }
    };
    let url = "http://api.twitch.tv/helix/chat/messages";
    let response = await fetch(url, payload);

    if (!response.ok) {
        return Response.json({
            status: response.status,
            error: 'oauth error?'
        }, {
            status: 500
        });
    }
    if (!response.headers?.get('content-type')?.includes('application/json')) {
        return Response.json({
            status: response.status,
            error: 'malformed json'
        }, {
            status: 500
        });
    }
    const json = await response.json();
    console.log(json);
    return
}

handler(message) {
  if (message === undefined) return;
// for (const heart in #hearts) if (message.startsWith(heart)) {
//     this.#commands.announce(message.substring(1).trim(), hearts[heart]);
//     return;
// }
  this.chat(message);
};

export default{
  async fetch(request, env, ctx){
  // constants declared, blah blah
  class Database{} // uses async fetch here too
  class TwitchChat{} // this is the class that contains those methods
  switch(request.method){} // switch on the method, with switch on pathnames as well within
  }
}