Body:
[`StreamingResponse` docs](https://fastapi.tiangolo.com/advanced/custom-response/?h=responses#streamingresponse) state:

> Takes an async generator or a normal generator/iterator

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

```py
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`

--- Comments ---

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

User: mirza-mohibul-hasan
Hi @casperdcl, thanks for raising this. I understand the issue and the root cause with async generators blocking without an await. If the fix isn’t already finalized, I’d be happy to work on this or help refine the docs/validate the example. Please let me know if that works for you.

User: casperdcl
fixed in fastapi#14681

Body:
[`StreamingResponse` docs](https://fastapi.tiangolo.com/advanced/custom-response/?h=responses#streamingresponse) state:

> Takes an async generator or a normal generator/iterator

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

```py
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`

--- Comments ---

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

User: mirza-mohibul-hasan
Hi @casperdcl, thanks for raising this. I understand the issue and the root cause with async generators blocking without an await. If the fix isn’t already finalized, I’d be happy to work on this or help refine the docs/validate the example. Please let me know if that works for you.

User: casperdcl
fixed in fastapi#14681

Body:
[`StreamingResponse` docs](https://fastapi.tiangolo.com/advanced/custom-response/?h=responses#streamingresponse) state:

> Takes an async generator or a normal generator/iterator

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

```py
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`

--- Comments ---

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

User: mirza-mohibul-hasan
Hi @casperdcl, thanks for raising this. I understand the issue and the root cause with async generators blocking without an await. If the fix isn’t already finalized, I’d be happy to work on this or help refine the docs/validate the example. Please let me know if that works for you.

User: casperdcl
fixed in fastapi#14681