async-local-storage.ts

import { AsyncLocalStorage } from 'node:async_hooks'

const useStorage = <E extends unknown>() => {
  const localStorage = new AsyncLocalStorage()
  return {
    store: <T>(env: E, callback: () => T): T => {
      return localStorage.run(env, callback)
    },
    get: (key: keyof E) => {
      const store = localStorage.getStore() as E
      return store[key]
    }
  }
}

type Env = {
  MY_KV: KVNamespace
}

const { store, get } = useStorage<Env>()

async function outSideOfHandler() {
  console.log(await get('MY_KV').get('key'))
}

export default {
  async fetch(req, env, ctx) {
    return store(env, async () => {
      env.MY_KV.put('key', 'foo')
      await outSideOfHandler()
      return new Response('Hi')
    })
  }
} satisfies ExportedHandler<Env>