What problem does it solve? Writing correct async Rust code is difficult: developers struggle with runtime selection, blocking the executor, channel design, deadlocks from holding locks across await points, and cryptic Send trait errors. This Skill provides structured guidance and working code patterns for building concurrent async applications with tokio. ## Core Features & Use Cases - Runtime & Task Management: Guidance on choosing tokio multi-thread vs current-thread runtimes, spawning tasks with tokio::spawn, spawn_blocking, and JoinSet for structured concurrency. - Channel Communication Patterns: Covers mpsc, oneshot, broadcast, and watch channels with actor-style request-response designs and select! multiplexing. - Error Diagnosis: A lookup table mapping common compiler and runtime errors (Send violations, nested runtimes, deadlocks, channel backpressure) to concrete fixes. - Use Case: When building a high-concurrency HTTP service that needs graceful shutdown, use this Skill to implement a CancellationToken-coordinated shutdown with Semaphore-based rate limiting and async stream processing pipelines. ## Quick Start Ask the AI to write a tokio-based async worker that receives requests over an mpsc channel, responds via oneshot, and shuts down gracefully on Ctrl+C.