你可以使用全局变量。下面的redis设置应该适用于nextJS，使用redis云免费示例，在免费计划中最多有30个连接。
代码：

import * as redis from 'redis';

const REDIS_USERNAME = process.env.REDIS_USERNAME;
const REDIS_PASSWORD = process.env.REDIS_PASSWORD;
const REDIS_HOST = process.env.REDIS_HOST;
const REDIS_PORT = process.env.REDIS_PORT;

let redisClient;
let redisClientPromise;

if (process.env.NEXT_PUBLIC_NODE_ENV === 'development') {
    if (!global._redisClientPromise) {
        redisClient = redis.createClient({
            url: `redis://${REDIS_USERNAME}:${REDIS_PASSWORD}@${REDIS_HOST}:${REDIS_PORT}`
        });
        redisClient.connect().then(() => {
            console.info(
                `NextJS Redis client connected..`
            );
        }).catch((error) => {
            console.error(`[ERROR] Couldn't connect to Redis client: ${error}`);
        });
        global._redisClientPromise = redisClient;
    }
    redisClientPromise = global._redisClientPromise
} else {
    redisClient = redis.createClient({
        url: `redis://${REDIS_USERNAME}:${REDIS_PASSWORD}@${REDIS_HOST}:${REDIS_PORT}`
    });
    redisClient.connect().then(() => {
        console.info(
            `NextJS Redis client connected..`
        );
    }).catch((error) => {
        console.error(`[ERROR] Couldn't connect to Redis client: ${error}`);
    });
    redisClientPromise = redisClient;
}

export default redisClientPromise;