@middy/warmup/index.js

const defaults = {
    isWarmingUp: (event)=>event.source === 'serverless-plugin-warmup'
};
const warmupMiddleware = (opt)=>{
    const options = {
        ...defaults,
        ...opt
    };
    const warmupMiddlewareBefore = (request)=>{
        if (options.isWarmingUp(request.event)) {
            return 'warmup';
        }
    };
    return {
        before: warmupMiddlewareBefore
    };
};
export default warmupMiddleware;