How can I make POST calls using fetch?

Hi, I am trying to make a post request using fetch to one of my functions but the console tells me it is unsupported with the following message:
POST http://localhost:7000/.netlify/functions/my_func 501 (Unsupported method ('POST'))

I am making an API call posting a json payload, and need to wait for it’s response in the function, thus did not want to use forms.

fetch("/.netlify/functions/my_func", {
  method: 'POST',
  headers: {
    Accept: "application/json",
  body: JSON.stringify(my_json)
.then(data =>  return data.json() });

exports.handler = async(event, context, callback) => {
  if (event.httpMethod !== "POST") {
    return { statusCode: 405, body: "Method Not Allowed" };
  return {
    statusCode: 200,
    body: "Ok"

Can you tell me more about how you are testing? It looks like you are posting to ‘localhost:7000’. What are you using to run your local dev server? Have you tried deploying your function to a site and testing there?