PUBLIC_BACKEND_SERVER_URL is not exported error During Docker Build Despite Being Set in .env File in SvelteKit Project

I'm working on a SvelteKit project and I'm encountering an issue where the PUBLIC_BACKEND_SERVER_URL environment variable, which I have defined in my .env file, is not being recognized during the Docker build process. Here are the details of the error and my setup:

Error log when running docker build -t svelte-frontend .:

2.803 x Build failed in 2.13s2.803 error during build:2.803 src/lib/posts/fetch-pagination.ts (3:9): "PUBLIC_BACKEND_SERVER_URL" is not exported by "virtual:$env/static/public", imported by "src/lib/posts/fetch-pagination.ts".2.803 file: /app/src/lib/posts/fetch-pagination.ts:3:92.803 2.803 1: import { get, type Writable } from "svelte/store";2.803 2: import { collectionObj } from "./store";2.803 3: import { PUBLIC_BACKEND_SERVER_URL } from "$env/static/public";2.803             ^2.803 

Code:

src/lib/fetch-pagination.ts

import { get, type Writable } from "svelte/store";import { collectionObj } from "./store";import { PUBLIC_BACKEND_SERVER_URL } from "$env/static/public";// Define the options for the fetch requestconst options = {    method: "POST",    headers: { "Content-Type": "application/json" },    body: JSON.stringify({...}),};// Fetch function to get paginated postsexport const fetchPaginatedPosts = async (key: string = "posts", last_id: string = "") => {  collectionObj.set(key);  console.log("de: ", get(collectionObj));  try {    const response = await fetch(      `${PUBLIC_BACKEND_SERVER_URL}/get-paginated`,      options    );    if (!response.ok) {      throw new Error("Network response was not ok");    }    const res = await response.json();    console.log("API call");    return res;  } catch (error) {    console.error(error);    throw error;  }};

.env File:

PUBLIC_BACKEND_SERVER_URL=http://localhost:1234

Dockerfile:

FROM node:20-alpine AS builderWORKDIR /appCOPY package*.json .RUN npm ciCOPY . .RUN npm run buildRUN npm prune --productionFROM node:20-alpineWORKDIR /appCOPY --from=builder /app/build build/COPY --from=builder /app/node_modules node_modules/COPY package.json .EXPOSE 3000ENV NODE_ENV=productionCMD ["node", "./build"]

The environment variables load correctly and the application works as expected when I run npm run dev. However, the build fails when trying to build the Docker image.

package.json:

"scripts": {"dev": "vite dev","build": "vite build","preview": "vite preview","check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json","check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch"    },

Questions:

1. Why is PUBLIC_BACKEND_SERVER_URL not being recognized by $env/static/public during the Docker build process?
2. Are there additional steps I need to take to ensure environment variables are properly imported during a Docker build in a SvelteKit project?
3. Is there something wrong with my Dockerfile setup that might be causing this issue?

Any insights or suggestions would be greatly appreciated. Thank you!