Using nestjs DI with class validator

Seems like a real pain in the brain...

There is a huge thread about this on github and other sites, many of them come down to using useContainer from the 'class-validator' but it does not work for me.

async function bootstrap() {
  const app = await NestFactory.create(ApplicationModule);
  useContainer(app, { fallback: true });
  await app.listen(3000);
}
bootstrap();

Here's the injectable:

@ValidatorConstraint({ name: 'uniqueOnDatabase', async: true })
@Injectable()
export class UniqueOnDatabase implements ValidatorConstraintInterface {
    constructor(
        private readonly userService: UserService,
    ) {}
    public async validate(val: any, args: ValidationArguments): Promise<boolean> {
        const user = await this.userService.retrieveOneByEmail(val);
        return !user;
    }

    public defaultMessage(args: ValidationArguments): string {
        return `User with such an email address already exists in the DB`;
    }
}

All I want to do is use my userService inside that UniqueOnDatabase class.

Here is the module where I am providing the UniqueOnDatabase:

import { Module, CacheModule } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import { CacheConfigService } from 'src/config/cache/config.service';
import { CacheService } from './services/cache.service';
import { CodeGenService } from './services/code-gen.service';
import { UserExistanceValidationPipe } from './pipes/user-existance.validation.pipe';
import { UsersModule } from 'src/users/users.module';
import { UniqueOnDatabase } from './validators/unique-on-database.validator';

@Module({
  providers: [
    CacheService,
    CodeGenService,
    UniqueOnDatabase,
  ],
  imports: [
    CacheModule.registerAsync({
      imports: [ConfigModule],
      useClass: CacheConfigService,
    }),
    UsersModule,
  ],
  exports: [
    CacheService,
    CodeGenService,
    UniqueOnDatabase,
  ],
})
export class SharedModule {}