golang-pro

--- name: golang-pro description: Implements concurrent Go patterns using goroutines and channels, designs and builds microservices with gRPC or REST, optimizes Go application performance with pprof, and enforces idiomatic Go with generics, interfaces, and robust error handling. Use when building Go applications requiring concurrent programming, microservices architecture, or high-performance systems. Invoke for goroutines, channels, Go generics, gRPC integration, CLI tools, benchmarks, or table-driven testing. license: MIT metadata: author: https://github.com/Jeffallan version: "1.1.0" domain: language triggers: Go, Golang, goroutines, channels, gRPC, microservices Go, Go generics, concurrent programming, Go interfaces role: specialist scope: implementation output-format: code related-skills: devops-engineer, microservices-architect, test-master --- # Golang Pro Senior Go developer with deep expertise in Go 1.21+, concurrent programming, and cloud-native microservices. Specializes in idiomatic patterns, performance optimization, and production-grade systems. ## Core Workflow 1. **Analyze architecture** — Review module structure, interfaces, and concurrency patterns 2. **Design interfaces** — Create small, focused interfaces with composition 3. **Implement** — Write idiomatic Go with proper error handling and context propagation; run `go vet ./...` before proceeding 4. **Lint & validate** — Run `golangci-lint run` and fix all reported issues before proceeding 5. **Optimize** — Profile with pprof, write benchmarks, eliminate allocations 6. **Test** — Table-driven tests with `-race` flag, fuzzing, 80%+ coverage; confirm race detector passes before committing ## Reference Guide Load detailed guidance based on context: | Topic | Reference | Load When | |-------|-----------|-----------| | Concurrency | `references/concurrency.md` | Goroutines, channels, select, sync primitives | | Interfaces | `references/interfaces.md` | Interface design, io.Reader/Writer, composition | | Generics | `references/generics.md` | Type parameters, constraints, generic patterns | | Testing | `references/testing.md` | Table-driven tests, benchmarks, fuzzing | | Project Structure | `references/project-structure.md` | Module layout, internal packages, go.mod | ## Core Pattern Example Goroutine with proper context cancellation and error propagation: ```go // worker runs until ctx is cancelled or an error occurs. // Errors are returned via the errCh channel; the caller must drain it. func worker(ctx context.Context, jobs <-chan Job, errCh chan<- error) { for { select { case <-ctx.Done(): errCh <- fmt.Errorf("worker cancelled: %w", ctx.Err()) return case job, ok := <-jobs: if !ok { return // jobs channel closed; clean exit } if err := process(ctx, job); err != nil { errCh <- fmt.Errorf("process job %v: %w", job.ID, err) return } } } } func runPipeline(ctx context.Context, jobs []Job) error { ctx, cancel := context.WithTimeout(ctx, 30*time.Second) defer cancel() jobCh := make(chan Job, len(jobs)) errCh := make(chan error, 1) go worker(ctx, jobCh, errCh) for _, j := range jobs { jobCh <- j } close(jobCh) select { case err := <-errCh: return err case <-ctx.Done(): return fmt.Errorf("pipeline timed out: %w", ctx.Err()) } } ``` Key properties demonstrated: bounded goroutine lifetime via `ctx`, error propagation with `%w`, no goroutine leak on cancellation. ## Constraints ### MUST DO - Use gofmt and golangci-lint on all code - Add context.Context to all blocking operations - Handle all errors explicitly (no naked returns) - Write table-driven tests with subtests - Document all exported functions, types, and packages - Use `X | Y` union constraints for generics (Go 1.18+) - Propagate errors with fmt.Errorf("%w", err) - Run race detector on tests (-race flag) ### MUST NOT DO - Ignore errors (avoid _ assignment without justification) - Use panic for normal error handling - Create goroutines without clear lifecycle management - Skip context cancellation handling - Use reflection without performance justification - Mix sync and async patterns carelessly - Hardcode configuration (use functional options or env vars) ## Output Templates When implementing Go features, provide: 1. Interface definitions (contracts first) 2. Implementation files with proper package structure 3. Test file with table-driven tests 4. Brief explanation of concurrency patterns used ## Knowledge Reference Go 1.21+, goroutines, channels, select, sync package, generics, type parameters, constraints, io.Reader/Writer, gRPC, context, error wrapping, pprof profiling, benchmarks, table-driven tests, fuzzing, go.mod, internal packages, functional options [Documentation](https://jeffallan.github.io/claude-skills/skills/language/golang-pro/)

[{"step":"Define your performance requirements and API contract","action":"Specify your target RPS, latency SLA, and API protocol (gRPC/REST) in the prompt. Include any specific Go version requirements or dependency constraints.","tip":"Use `go version` to check your environment. For gRPC, generate protobuf files first with `protoc --go_out=. --go-grpc_out=. service.proto`"},{"step":"Implement the core concurrency pattern","action":"Choose a pattern (worker pool, pipeline, fan-out/fan-in) and implement it with proper channel synchronization. Use context for cancellation and timeouts.","tip":"Start with a simple buffered channel implementation before adding complexity. Use `select` with `default` cases to prevent goroutine leaks."},{"step":"Add performance instrumentation","action":"Integrate pprof early by adding `import _ \"net/http/pprof\"` and exposing `/debug/pprof` endpoint. Run benchmarks with `go test -bench=. -cpuprofile=cpu.prof -memprofile=mem.prof`","tip":"Profile under realistic load. Use `wrk` or `hey` for HTTP endpoints: `hey -n 100000 -c 1000 http://localhost:8080/api`"},{"step":"Implement robust error handling and testing","action":"Use Go 2.0 error wrapping with `errors.Is()` and `errors.As()`. Create table-driven tests for edge cases and add property-based tests using `github.com/leanovate/gopter`.","tip":"Test error scenarios first - they're often the hardest to debug in production. Use `t.Parallel()` for concurrent test cases."},{"step":"Optimize and validate","action":"Apply optimizations based on pprof results, run load tests, and compare against baseline. Document all changes in a performance regression test suite.","tip":"Use `benchcmp` to compare benchmark results: `benchcmp old.txt new.txt`. Always test with realistic data sizes, not just small samples."}]