```python
from fastapi import FastAPI, Request, Depends
import helpers
import asyncio

app = FastAPI()

billing = helpers.BillingClient()


def get_billing() -> helpers.BillingClient:
    """FastAPI dependency providing the billing client."""
    return billing


@app.post("/charges", status_code=201)
async def create_charge(
    request: Request,
    client: helpers.BillingClient = Depends(get_billing),
):
    data = await request.json()
    amount = data["amount"]
    receipt = await asyncio.to_thread(client.charge, amount)
    return {"receipt": receipt}
```