What problem does it solve? Writing concurrent Go code without leaks or data races is error-prone: unbuffered channels combined with early returns strand goroutines forever, raw WaitGroups cannot propagate errors, and tests without the race detector prove nothing. This Skill provides verified patterns and review rules for goroutines, channels, errgroup, and context propagation in Go 1.26. ## Core Features & Use Cases - errgroup fan-out patterns: Bounded parallel work with SetLimit, first-error propagation, and automatic context cancellation via errgroup.WithContext. - Leak prevention and diagnosis: Fixes the documented unbuffered-channel-plus-early-return pitfall and covers the Go 1.26 goroutineleak pprof profile for detecting stranded goroutines. - Context propagation rules: Enforces ctx as the first parameter, strict cancellation handling, and correct use of WithTimeout and WithValue. - Use Case: When implementing a service that fetches hundreds of URLs in parallel, apply the errgroup template with SetLimit and per-index result slots to get bounded, cancellable, leak-free concurrency, then validate with go test -race. ## Quick Start Ask the agent to implement a bounded parallel fetch over a list of URLs using errgroup with context cancellation and then run the tests with the race detector enabled.
