Token service with constructor

TokenService.ts

export class TokenService {
  private jwt_secret: string;

  constructor() {
    if (!process.env.JWT_SECRET) {
      throw new Error('JWT secret not found in environment variables!');
    }
    this.jwt_secret = process.env.JWT_SECRET;
  }

  public verify(token: string) {
    // Implementation...
  }

  public sign(payload) {
    // Implementation...
  }
}

const tokenService = new TokenService();