# thread 'tokio-runtime-worker' panicked at 'Cannot drop a runtime in a context where blocking is not allowed'

- **ID:** `rust/tokio-runtime-shutdown-timeout`
- **Domain:** rust
- **Category:** runtime_error
- **Verification:** ai_generated
- **Fix Rate:** 82%

## Root Cause

Attempting to drop a Tokio runtime inside an asynchronous context (e.g., inside a future or task) where blocking is prohibited, often due to incorrect runtime nesting or shutdown.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| tokio 1.25.0 | active | — | — |
| tokio 1.30.0 | active | — | — |
| tokio 1.35.0 | active | — | — |

## Workarounds

1. **Ensure the runtime is dropped outside of any async context, e.g., by storing it in a struct and dropping it in a synchronous scope.** (85% success)
   ```
   Ensure the runtime is dropped outside of any async context, e.g., by storing it in a struct and dropping it in a synchronous scope.
   ```
2. **Use `tokio::runtime::Runtime::shutdown_timeout` to gracefully shut down before dropping.** (80% success)
   ```
   Use `tokio::runtime::Runtime::shutdown_timeout` to gracefully shut down before dropping.
   ```

## Dead Ends

- **** — Forgetting the runtime leaks resources and doesn't fix the underlying issue; the panic still occurs on drop. (90% fail)
- **** — The panic is caused by the drop logic, not by ownership; Arc doesn't prevent the drop from happening. (85% fail)
- **** — `block_on` itself blocks, which may trigger the same panic if called from an async context. (75% fail)