api.js

class ApiCache {
  constructor() {
    this.cache = {};
  }

  setupCache(cache) {
    this.cache = cache;
    console.log(this.cache);
  }
}

const cache = new ApiCache();

export const startCache = inst => cache.setupCache(inst);

server.js

import Cache from "../state/api/cache/redisCacheClient";
import { cacheInstance } from "../state/api/cache/redisCache";

const cache = new Cache(cacheInstance);
startCache(cache);