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

app = FastAPI()

billing = helpers.BillingClient()


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


@app.post("/charges", status_code=status.HTTP_201_CREATED)
async def create_charge(
    payload: dict, billing: helpers.BillingClient = Depends(get_billing)
):
    """
    Charge the given amount and return a receipt id.
    """
    amount = payload["amount"]
    receipt = await asyncio.to_thread(billing.charge, amount)
    return {"receipt": receipt}
```