How to Inject configService in main.ts ?

config.module.ts

import { Module } from '@nestjs/common';
import { ConfigService } from './config.service';

@Module({
  providers: [
    {
      provide: ConfigService,
      useValue: new ConfigService(`${process.env.NODE_ENV}.env`),
    },
  ],
  exports: [ConfigService],
})
export class ConfigModule {}

config.service.ts

import * as dotenv from 'dotenv';
import * as fs from 'fs';

export class ConfigService {
  private readonly envConfig: { [key: string]: string };

  constructor(filePath: string) {
    this.envConfig = dotenv.parse(fs.readFileSync(filePath));
  }

  get(key: string): string {
    return this.envConfig[key];
  }
  getDbType() {
    return ('postgres' as 'postgres');
  }
}

main.ts

// Load ENV_VARIABLES
import * as dotenv from 'dotenv';
dotenv.config();
import { NestFactory } from '@nestjs/core';
import { Logger, ValidationPipe } from '@nestjs/common';
import { AppModule } from './app.module';
import {ConfigService} from './config/config.service';

import * as helmet from 'helmet';

async function bootstrap() {
  const config: ConfigService = new ConfigService(`${process.env.NODE_ENV}.env`);
  const app = await NestFactory.create(AppModule);

  const HTTP_PORT = config.get('HTTP_PORT');

  // Use Middleware
  app.enableCors();
  app.use(helmet());

  /* Use Validation on all endpoints with a global validation Pipe */
  app.useGlobalPipes(new ValidationPipe());

  await app.listen(HTTP_PORT);

  Logger.log(`App running on port ${HTTP_PORT}`, 'Application Bootstrap');
}
bootstrap();