How do you write a minimal ASGI application that works with Uvicorn without any framework?

# main.py - minimal HTTP ASGI app
async def app(scope, receive, send):
    assert scope["type"] == "http"

    # Read the request body
    body = b""
    more_body = True
    while more_body:
        message = await receive()
        body += message.get("body", b"")
        more_body = message.get("more_body", False)

    # Send the HTTP response
    response_body = b"Hello, world!"
    await send({
        "type": "http.response.start",
        "status": 200,
        "headers": [
            (b"content-type", b"text/plain"),
            (b"content-length", str(len(response_body)).encode()),
        ],
    })
    await send({
        "type": "http.response.body",
        "body": response_body,
    })

# Run: uvicorn main:app

# Streaming response - send body in multiple chunks
async def streaming_app(scope, receive, send):
    assert scope["type"] == "http"
    await send({
        "type": "http.response.start",
        "status": 200,
        "headers": [(b"content-type", b"text/plain")],
    })
    for chunk in [b"Hello", b", ", b"world!"]:
        await send({
            "type": "http.response.body",
            "body": chunk,
            "more_body": True,  # indicates more chunks are coming
        })
    await send({"type": "http.response.body", "body": b"", "more_body": False})