Example of env file with zod validation (S/O to Matt Pocok : https://www.youtube.com/watch?v=q1im-hMlKhM)

zod_env.ts

import { z } from "zod";

const envVariables = z.object({
  DATABASE_URL: z.string(),
  CUSTOM_STUFF: z.string(),
});

export const ENV = envVariables.parse(process.env);

declare global {
  namespace NodeJS {
    interface ProcessEnv
      extends z.infer<typeof envVariables> {}
  }
}