How to get the JWT's secretOrKey from remote in NestJS?

Question

Here is my code to verify incoming request using JWT in NestJS:

import { ExtractJwt, Strategy } from 'passport-jwt';
import { PassportStrategy } from '@nestjs/passport';
import { Injectable } from '@nestjs/common';

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor() {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      ignoreExpiration: false,
      secretOrKey: 'test',
    });
  }

  async validate(payload: any) {
    return {
      userId: payload.sub,
      username: payload.username,
    };
  }
}

It works well when I set the secretOrKey to 'test' (define the secretOrKey locally). For security reason, I want to read the secretOrKey from the key/value in Consul (or Redis):

import { ExtractJwt, Strategy } from 'passport-jwt';
import { PassportStrategy } from '@nestjs/passport';
import { Injectable } from '@nestjs/common';
import { listSecret } from './constants';

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor(private readonly Secret: listSecret) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      ignoreExpiration: false,
      secretOrKey: Secret.listSec(),
    });
  }

  async validate(payload: any) {
    return {
      userId: payload.sub,
      username: payload.username,
    };
  }
}

Here is the listSecret:

import { Consul } from '../Consul';
import { Inject, Injectable } from '@nestjs/common';
@Injectable()
export class listSecret {
  constructor(
    private consul: Consul,
  ) {}
  async listSec() {
    const JWT_KEY = await this.consul.ConsulUse(
      'https://192.168.1.1:8501/v1/kv/jwt',
    );
    return JWT_KEY;
  }
}

When I run the app to send a request with the JWT, I get the :

{
    "statusCode": 401,
    "message": "Unauthorized"
}

It seems that the secretOrKey could not get the right value (I guess it could have a 'Promise { < pending > }' in return). So, I think it would use 'async/await' in the constructor (jwt.strategy.ts), but I can not find a way to do that (the Consul is working well).

Thanks