StreamingResponse doc example needs correction

[casperdcl]

StreamingResponse docs state:

Takes an async generator or a normal generator/iterator

However based on Kludex/starlette#1776 (comment) async generetors need something awaited to work:

import asyncio
from time import sleep
from fastapi import FastAPI
from fastapi.responses import StreamingResponse

app = FastAPI()

async def fake_video_streamer():
    for i in range(10):
        sleep(0.1)
        yield b"some fake video bytes"
        # await asyncio.sleep(0)  # <-- uncomment to fix example

@app.get("/")
async def main():
    """
    this is as per
    https://fastapi.tiangolo.com/advanced/custom-response/?h=responses#streamingresponse
    but does not to work (blocks for 1 sec, then returns all chunks at once):
      curl -sNo- localhost:8000
      wget -qO- localhost:8000
    """
    return StreamingResponse(fake_video_streamer())

• uvicorn==0.40.0
• fastapi==0.128.0

[casperdcl]

It seems based on Kludex/starlette#1776 (comment) that await asyncio.sleep(0) needs to be added to the documented example to work.