prepass.js

import React, { useContext } from 'react'
import ReactDOM from 'react-dom/server'
import ssrPrepass from 'react-ssr-prepass'

const Context = React.createContext()

const asyncFoo = async () => 'foo'

function MyComponent() {
  const tracker = useContext(Context)
  if (!tracker.resolved) {
    throw asyncFoo().then(result => {
      tracker.resolved = result
    })
  }
  return tracker.resolved
}

async function main() {
  const tracker = {}
  const app = (
    <Context.Provider value={tracker}>
      <MyComponent />
    </Context.Provider>
  )

  await ssrPrepass(app)

  console.log(ReactDOM.renderToString(app))
}

main().catch(error =>
  setTimeout(() => {
    throw error
  }),
)