next.js/test/e2e/app-dir/actions-streaming/app/readable-stream/api/route.ts

import { setTimeout } from 'timers/promises'

const loremIpsum =
  'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt.\n'

export async function GET() {
  const encoder = new TextEncoder()

  const stream = new ReadableStream({
    async start(controller) {
      for (let i = 0; i < 50; i++) {
        await setTimeout(100)
        controller.enqueue(encoder.encode(loremIpsum))
      }
      controller.close()
    },
  })

  return new Response(stream, { headers: { 'Content-Type': 'text/plain' } })
}