What is the difference between tokio::select! and futures::select!?

Question

Accepted Answer

**tokio::select!** — Tokio-specific. **futures::select!** — runtime-agnostic.

**tokio::select!:**
- Tokio runtime.
- Better ergonomics.
- Cancellation safety.

**futures::select!:**
- Runtime-agnostic.
- More verbose.
- Less safe.

```rust
tokio::select! {
    val = fetch_a() => println!("A: {}", val),
    val = fetch_b() => println!("B: {}", val),
}

futures::select! {
    val = fetch_a().fuse() => println!("A: {}", val),
    val = fetch_b().fuse() => println!("B: {}", val),
    complete => println!("Done"),
    default => (),
}
```

**Key:** tokio::select! for Tokio, futures::select! for portability.

Rust: What is the difference between tokio::select! and futures::select!?