nestjs env variable undefined before class definition - node.js

Question

I am working on app written in nestjs and trying to implement WebSocket. One problem i am having is with use of env variables. In the gateway file where i define my WebSocket implementation we have need of using PORT from env before class is defined:
console.log(process.env.WSPORT) // undefined
setInterval(() => {
console.log((process.env.WSPORT) // after few logs its becoming accessible
}, 100)
#WebSocketGateway(process.env.WSPORT)
export class ExportFeedsGateway implements OnGatewayInit {
I tried to debug what is going on, and it seems to be related with when it is invoked as few moments later this variable becomes available for use.
app.module.ts
import { Module } from '#nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { ConfigModule } from '#nestjs/config';
import { ExportFeedsGateway } from './modules/exportFeeds/export-feeds.gateway';
#Module({
imports: [ConfigModule.forRoot({ expandVariables: true })],
controllers: [AppController],
providers: [AppService, ExportFeedsGateway],
})
export class AppModule {}
export-feeds.gateway.ts
import { OnGatewayInit, WebSocketGateway } from '#nestjs/websockets';
#WebSocketGateway(process.env.WSPORT)
export class ExportFeedsGateway implements OnGatewayInit {
...
}
how to modify this code to make sure that WSPORT is not undefined when its passed to WebSocketGateway decorator?
----- EDIT
I was hoping to utilise nestjs code to access this variable rather then use packages like dotenv
main.ts
import { NestFactory } from '#nestjs/core';
import { AppModule } from './app.module';
import { WsAdapter } from '#nestjs/platform-ws';
const PORT = process.env.PORT;
async function bootstrap() {
const app = await NestFactory.create(AppModule, { cors: true });
app.useWebSocketAdapter(new WsAdapter(app));
await app.listen(PORT);
}
bootstrap();

Answer 1

you need to inject that env var in the shell, not via .env. Or use the dotenv by yourself as the first line at your main.ts

Answer 2

I did deeper research and the problem i was having is actually result of trying to use WebSocket implementation (gateway) as standalone import. So the answer and solution to the problem is to create module first
import { Module } from '#nestjs/common';
import { ExportFeedsGateway } from './export-feeds.gateway';
#Module({
providers: [ExportFeedsGateway],
exports: [ExportFeedsGateway],
})
export class ExportFeedsModule {}
This is a proper way of doing things as far as nestjs is concerned.
After this step module should be imported instead of gateway and env variables are accessible through process.env.something
#WebSocketGateway(Number(process.env.EXPORT_FEEDS_PORT))
export class ExportFeedsGateway implements OnGatewayInit {
...
}