Sveltekit +page.server.ts cannot reach backend on same machine

I have a backend server in GO running on localhost:8081 exposing a couple of endpoints. These endpoints are nicely reachable with requests via CURL, Postman, ...

I am trying to build a SvelteKit frontend application running on dev default port localhost:5137. In the +page.server.ts file I have a load function trying to contact one of the endpoints on localhost:8081, but it does not work. I only ever get this error:

TypeError: fetch failed    ...  cause: Error: connect ECONNREFUSED 127.0.0.1:8081      at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1161:16) {    errno: -4078,    code: 'ECONNREFUSED',    syscall: 'connect',    address: '127.0.0.1',    port: 8081  }

The contents of my +page.server.svelte - load function looks like this:

export async function load({fetch}) {    const res = await fetch('http://localhost:8081/api/...');    return await res.json();}

Even checked and added the missing origin headers inside the hooks.server.svelte file:

export const handleFetch: HandleFetch = async({request, fetch, event}) => {    request.headers.set('Origin', event.url.origin);    return fetch(request)};

But I cannot seem to get rid of this error. Other endpoints from external public apis work nicely and I can retrieve data from them.

If anyone has any ideas, those would be greatly appreciated. I am all googled out...

Here is the list of used dependencies:

• NPM v9.6.4

• node v16.13.0

• "@sveltejs/adapter-auto": "^2.0.0",

• "@sveltejs/kit": "^1.5.0",

• "@typescript-eslint/eslint-plugin": "^5.45.0",

• "@typescript-eslint/parser": "^5.45.0",

• "eslint": "^8.28.0",

• "eslint-config-prettier": "^8.5.0",

• "eslint-plugin-svelte3": "^4.0.0",

• "prettier": "^2.8.0",

• "prettier-plugin-svelte": "^2.8.1",

• "svelte": "^3.54.0",

• "svelte-check": "^3.0.1",

• "tslib": "^2.4.1",

• "typescript": "^4.9.3",

• "vite": "^4.0.0",

• "vitest": "^0.25.3"

I was expecting the endpoint to be reachable like any other external public API and return the expected data so I also:

• checked various CORS settings
• added missing headers