import asyncio
import uvicorn
from starlette.applications import Starlette
from starlette.routing import Route
from sse_starlette.sse import EventSourceResponse

async def numbers(minimum, maximum):
    for i in range(minimum, maximum + 1):
        await asyncio.sleep(0.9)
        yield dict(data=i)

async def sse(request):
    generator = numbers(1, 5)
    return EventSourceResponse(generator)

routes = [
    Route("/", endpoint=sse)
]

app = Starlette(debug=True, routes=routes)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000, log_level='info')

async def endless(req: Request):
    async def event_publisher():
        i = 0
        try:
          while True:
              disconnected = await req.is_disconnected()
              if disconnected:
                  _log.info(f"Disconnecting client {req.client}")
                  break
              i += 1
              yield dict(data=i)
              await asyncio.sleep(0.2)
          _log.info(f"Disconnected from client {req.client}")
        except asyncio.CancelledError as e:
          _log.info(f"Disconnected from client (via refresh/close) {req.client}")
          # Do any other cleanup, if any
          raise e
    return EventSourceResponse(event_publisher())

make test