Hey there, I have setup a simple application with a backend/frontend/database

I have set the variable for my front end to be RAILWAY_PRIVATE_DOMAIN it is called NEXT_PUBLIC_BACKEND_URL I read another thread saying that I had to add an arg into my dockerfile so I did that:

ARG NEXT_PUBLIC_BACKEND_URL

Getting the variable:

"use client";
import { Weather } from "./podcast-models";

export default class PodcastService {
  private _baseUrl: string;

  constructor() {
    this._baseUrl = process.env.NEXT_PUBLIC_BACKEND_URL ?? "";
  }

  public async getWeather(): Promise<Weather[]> {
    let response = await fetch(`${this._baseUrl}/weather`);
    return (await response.json()) as Weather[];
  }
}

but when the request is sent the url is set to the frontend servive (which probably means that its defaulting to empty string) any help would be appreciated