golang-data-structures
Golang data structures — slices (internals, capacity growth, preallocation, slices package), maps (internals, hash buckets, maps package), arrays, container/list/heap/ring, strings.Builder vs bytes.Buffer, generic collections, pointers (unsafe.Pointer, weak.Pointer), and copy semantics. Use when choosing or optimizing Go data structures, implementing generic containers, using container/ packages, unsafe or weak pointers, or questioning slice/map internals. Not for applying optimization patterns once profiling has identified a bottleneck (→ See samber/cc-skills-golang@golang-performance skill).
- Installs
- 40.5K
- Last 24h
- +163
- Trending rank
- #1430
- Security
- Pass
Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/samber/cc-skills-golang --skill golang-data-structures- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads golang-data-structures automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
Persona: You are a Go engineer who understands data structure internals. You choose the right structure for the job — not the most familiar one — by reasoning about memory layout, allocation cost, and access patterns.
Go Data Structures
Built-in and standard library data structures: internals, correct usage, and selection guidance.
- For safety pitfalls (nil maps, append aliasing, defensive copies) see
samber/cc-skills-golang@golang-safetyskill. - For channels and sync primitives see
samber/cc-skills-golang@golang-concurrencyskill. - For string/byte/rune choice see
samber/cc-skills-golang@golang-design-patternsskill.
Best Practices Summary
- Preallocate slices and maps with
make(T, 0, n)/make(map[K]V, n)when size is known or estimable — avoids repeated growth copies and rehashing - Arrays SHOULD be preferred over slices only for fixed, compile-time-known sizes (hash digests, IPv4 addresses, matrix dimensions)
- NEVER rely on slice capacity growth timing — the growth algorithm changed between Go versions and may change again; your code should not depend on when a new backing array is allocated
- Use
container/heapfor priority queues,container/listonly when frequent middle insertions are needed,container/ringfor fixed-size circular buffers strings.BuilderMUST be preferred for building strings;bytes.BufferMUST be preferred for bidirectional I/O (implements bothio.Readerandio.Writer)- Generic data structures SHOULD use the tightest constraint possible —
comparablefor keys, custom interfaces for ordering unsafe.PointerMUST only follow the 6 valid conversion patterns from the Go spec — NEVER store in auintptrvariable across statementsweak.Pointer[T](Go 1.24+) SHOULD be used for caches and canonicalization maps to allow GC to reclaim entries
Slice Internals
A slice is a 3-word header: pointer, length, capacity. Multiple slices can share a backing array (→ see samber/cc-skills-golang@golang-safety for aliasing traps and the header diagram).
Capacity Growth
- < 256 elements: capacity doubles
-
= 256 elements: grows by ~25% (
newcap += (newcap + 3*256) / 4) - Each growth copies the entire backing array — O(n)
Preallocation
// Exact size known
users := make([]User, 0, len(ids))
// Approximate size known
results := make([]Result, 0, estimatedCount)
// Pre-grow before bulk append (Go 1.21+)
s = slices.Grow(s, additionalNeeded)
slices Package (Go 1.21+)
Key functions: Sort/SortFunc, BinarySearch, Contains, Compact, Grow. For Clone, Equal, DeleteFunc → see samber/cc-skills-golang@golang-safety skill.
Slice Internals Deep Dive — Full slices package reference, growth mechanics, len vs cap, header copying, backing array aliasing.
Map Internals
Maps are hash tables with 8-entry buckets and overflow chains. They are reference types — assigning a map copies the pointer, not the data.
Preallocation
m := make(map[string]*User, len(users)) // avoids rehashing during population
maps Package Quick Reference (Go 1.21+)
| Function | Purpose |
|---|---|
Collect (1.23+) | Build map from iterator |
Insert (1.23+) | Insert entries from iterator |
All (1.23+) | Iterator over all entries |
Keys, Values | Iterators over keys/values |
For Clone, Equal, sorted iteration → see samber/cc-skills-golang@golang-safety skill.
Map Internals Deep Dive — How Go maps store and hash data, bucket overflow chains, why maps never shrink (and what to do about it), comparing map performance to alternatives.
Arrays
Fixed-size, value types. Copied entirely on assignment. Use for compile-time-known sizes:
type Digest [32]byte // fixed-size, value type
var grid [3][3]int // multi-dimensional
cache := map[[2]int]Result{} // arrays are comparable — usable as map keys
Prefer slices for everything else — arrays cannot grow and pass by value (expensive for large sizes).
container/ Standard Library
| Package | Data Structure | Best For |
|---|---|---|
container/list | Doubly-linked list | LRU caches, frequent middle insertion/removal |
container/heap | Min-heap (priority queue) | Top-K, scheduling, Dijkstra |
container/ring | Circular buffer | Rolling windows, round-robin |
bufio | Buffered reader/writer/scanner | Efficient I/O with small reads/writes |
Container types use any (no type safety) — consider generic wrappers. Container Patterns, bufio, and Examples — When to use each container type, generic wrappers to add type safety, and bufio patterns for efficient I/O.
strings.Builder vs bytes.Buffer
Use strings.Builder for pure string concatenation (avoids copy on String()), bytes.Buffer when you need io.Reader or byte manipulation. Both support Grow(n). Details and comparison
Generic Collections (Go 1.18+)
Use the tightest constraint possible. comparable for map keys, cmp.Ordered for sorting, custom interfaces for domain-specific ordering.
type Set[T comparable] map[T]struct{}
func (s Set[T]) Add(v T) { s[v] = struct{}{} }
func (s Set[T]) Contains(v T) bool { _, ok := s[v]; return ok }
Writing Generic Data Structures — Using Go 1.18+ generics for type-safe containers, understanding constraint satisfaction, and building domain-specific generic types.
Pointer Types
| Type | Use Case | Zero Value |
|---|---|---|
*T | Normal indirection, mutation, optional values | nil |
unsafe.Pointer | FFI, low-level memory layout (6 spec patterns only) | nil |
weak.Pointer[T] (1.24+) | Caches, canonicalization, weak references | N/A |
Pointer Types Deep Dive — Normal pointers, unsafe.Pointer (the 6 valid spec patterns), and weak.Pointer[T] for GC-safe caches that don't prevent cleanup.
Copy Semantics Quick Reference
| Type | Copy Behavior | Independence |
|---|---|---|
int, float, bool, string | Value (deep copy) | Fully independent |
array, struct | Value (deep copy) | Fully independent |
slice | Header copied, backing array shared | Use slices.Clone |
map | Reference copied | Use maps.Clone |
channel | Reference copied | Same channel |
*T (pointer) | Address copied | Same underlying value |
interface | Value copied (type + value pair) | Depends on held type |
Third-Party Libraries
For advanced data structures (trees, sets, queues, stacks) beyond the standard library:
emirpasic/gods— comprehensive collection library (trees, sets, lists, stacks, maps, queues)deckarep/golang-set— thread-safe and non-thread-safe set implementationsgammazero/deque— fast double-ended queue
When using third-party libraries, refer to their official documentation and code examples for current API signatures.
- For Go package docs, symbols, versions, importers, and known vulnerabilities, → See
samber/cc-skills-golang@golang-pkg-go-devskill (godig) — prefer it over Context7 for Go package facts. - To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See
samber/cc-skills-golang@golang-goplsskill (gopls). - Context7 remains a fallback for docs not indexed on pkg.go.dev.
Cross-References
- → See
samber/cc-skills-golang@golang-performanceskill for struct field alignment, memory layout optimization, and cache locality - → See
samber/cc-skills-golang@golang-safetyskill for nil map/slice pitfalls, append aliasing, defensive copying,slices.Clone/Equal - → See
samber/cc-skills-golang@golang-concurrencyskill for channels,sync.Map,sync.Pool, and all sync primitives - → See
samber/cc-skills-golang@golang-design-patternsskill forstringvs[]bytevs[]rune, iterators, streaming - → See
samber/cc-skills-golang@golang-structs-interfacesskill for struct composition, embedding, and generics vsany - → See
samber/cc-skills-golang@golang-code-styleskill for slice/map initialization style
Common Mistakes
| Mistake | Fix |
|---|---|
| Growing a slice in a loop without preallocation | Each growth copies the entire backing array — O(n) per growth. Use make([]T, 0, n) or slices.Grow |
Using container/list when a slice would suffice | Linked lists have poor cache locality (each node is a separate heap allocation). Benchmark first |
bytes.Buffer for pure string building | Buffer's String() copies the underlying bytes. strings.Builder avoids this copy |
unsafe.Pointer stored as uintptr across statements | GC can move the object between statements — the uintptr becomes a dangling reference |
| Large struct values in maps (copying overhead) | Map access copies the entire value. Use map[K]*V for large value types to avoid the copy |
References
FAQ
What does the golang-data-structures skill do?
Golang data structures — slices (internals, capacity growth, preallocation, slices package), maps (internals, hash buckets, maps package), arrays, container/list/heap/ring, strings.Builder vs bytes.Buffer, generic collections, pointers (unsafe.Pointer, weak.Pointer), and copy semantics. Use when choosing or optimizing Go data structures, implementing generic containers, using container/ packages, unsafe or weak pointers, or questioning slice/map internals. Not for applying optimization patterns once profiling has identified a bottleneck (→ See samber/cc-skills-golang@golang-performance skill).
How do I install golang-data-structures?
Run npx skills add https://github.com/samber/cc-skills-golang --skill golang-data-structures in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/golang-data-structures/ (personal) or .claude/skills/golang-data-structures/ (project).
Which AI agents can use golang-data-structures?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is golang-data-structures safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk passed; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains golang-data-structures?
It is published by samber in samber/cc-skills-golang. It has 40,458 recorded installs.
More from samber/cc-skills-golang
golang-code-style
samber/cc-skills-golang
Golang code style conventions — line length and breaking, variable declarations, control flow clarity, when comments help vs hurt. Use when writing or reviewing Go code, asking about style or clarity, or establishing project coding standards. Not for naming conventions (→ See samber/cc-skills-golang@golang-naming skill), linter configuration (→ See samber/cc-skills-golang@golang-lint skill), or doc comments (→ See samber/cc-skills-golang@golang-documentation skill).
golang-testing
samber/cc-skills-golang
Production-ready Golang tests — table-driven tests, testify suites and mocks, parallel tests, fuzzing, fixtures, goroutine leak detection with goleak, snapshot testing, code coverage, integration tests, idiomatic test naming. Use when writing or reviewing Go tests, choosing a testing approach, setting up Go test CI, or debugging flaky/slow tests. For testify-specific APIs see samber/cc-skills-golang@golang-stretchr-testify; for measurement methodology see samber/cc-skills-golang@golang-benchmark.
golang-error-handling
samber/cc-skills-golang
Idiomatic Golang error handling — creation, wrapping with %w, errors.Is/As, errors.Join, custom error types, sentinel errors, panic/recover, the single handling rule, structured logging with slog, HTTP request logging middleware, and samber/oops for production errors. Built to make logs usable at scale with log aggregation 3rd-party tools. Apply when creating, wrapping, inspecting, or logging errors in Go code. For samber/oops specifics → See samber/cc-skills-golang@golang-samber-oops skill; for slog handler ecosystem → See samber/cc-skills-golang@golang-samber-slog skill.
golang-security
samber/cc-skills-golang
Security best practices and vulnerability prevention for Golang — injection (SQL, command, XSS), cryptography, path traversal, SSRF and HTTP security headers, cookies, secrets management, memory safety, PII in logs, STRIDE/DREAD threat modeling, plus gosec SAST, race detection, and fuzz testing. Apply when writing, reviewing, or auditing Go code for security, or when touching crypto, file or network I/O, secrets, user input, or authentication. Not for non-exploitable defensive bugs such as nil panics or slice aliasing (→ See samber/cc-skills-golang@golang-safety skill), dependency vulnerability scanning with govulncheck (→ See samber/cc-skills-golang@golang-dependency-management skill), or wiring security scanners into CI pipelines (→ See samber/cc-skills-golang@golang-continuous-integration skill).
golang-design-patterns
samber/cc-skills-golang
Idiomatic Golang design patterns — functional options, constructor APIs, init() and global-state avoidance, enums, panic vs error decisions, resource management and lifecycle, graceful shutdown, timeouts and retries, streaming and iterators, and architecture styles (clean, hexagonal, DDD, flat). Apply when choosing between architectural patterns, implementing functional options, designing constructor APIs, setting up graceful shutdown, applying resilience patterns, or asking which idiomatic Go pattern fits a specific problem. Not for wiring a DI container or comparing DI libraries (→ See samber/cc-skills-golang@golang-dependency-injection skill), nor for error wrapping, errors.Is/As, or logging mechanics (→ See samber/cc-skills-golang@golang-error-handling skill).
golang-performance
samber/cc-skills-golang
Golang performance optimization patterns and methodology - if X bottleneck, then apply Y. Covers allocation reduction, CPU efficiency, memory layout, GC tuning, pooling, caching, and hot-path optimization. Use when profiling or benchmarks have identified a bottleneck and you need the right optimization pattern to fix it. Also use when performing performance code review to suggest improvements or benchmarks that could help identify quick performance gains. Not for measurement methodology (→ See samber/cc-skills-golang@golang-benchmark skill) or debugging workflow (→ See samber/cc-skills-golang@golang-troubleshooting skill).
Popular backend & apis skills
entra-app-registration
microsoft/azure-skills
Guides Microsoft Entra ID app registration, OAuth 2.0 authentication, and MSAL integration. USE FOR: create app registration, register Azure AD app, configure OAuth, set up authentication, add API permissions, generate service principal, MSAL example, console app auth, Entra ID setup, Azure AD authentication. DO NOT USE FOR: Key Vault secrets (use azure-keyvault-expiration-audit), general Azure resource security guidance.
google-agents-cli-adk-code
google/agents-cli
This skill should be used when the user wants to "write agent code", "build an agent with ADK", "add a tool", "create a callback", "define an agent", "use state management" — in a project that needs ADK (Agent Development Kit) API patterns and code examples. It provides a quick reference for agent types, tool definitions, orchestration patterns, callbacks, state management, the graph Workflow API, and reference recipes to study. Do NOT use for scaffolding (use google-agents-cli-scaffold) or deployment (use google-agents-cli-deploy).
embedded-captions
heygen-com/hyperframes
Add captions or subtitles to an existing single-subject talking-head video without editing the footage. Use for plain verbatim captions, cinematic captions embedded behind the subject, VFX captions, “炸/特效/酷炫字幕,” or a named identity from the 35-style catalog. Route by visual identity, not by backend engine. The quiet anchor rail is the default; embed every word only when the user explicitly wants a fully cinematic treatment. The workflow runs locally end to end, including transcription and subject matting; split multi-shot footage before applying it.
entra-agent-id
microsoft/azure-skills
Provision Microsoft Entra Agent Identity Blueprints, BlueprintPrincipals, and per-instance Agent Identities via Microsoft Graph, and configure OAuth 2.0 token exchange (fmipath, OBO, cross-tenant) including the Microsoft Entra SDK for AgentID sidecar. USE FOR: Agent Identity Blueprint, BlueprintPrincipal, agent OAuth, fmipath token exchange, agent OBO, Workload Identity Federation for agents, polyglot agent auth, Microsoft.Identity.Web.AgentIdentities. DO NOT USE FOR: standard Entra app registration (use entra-app-registration), Microsoft Foundry agent authoring (use microsoft-foundry).
neon
neondatabase/agent-skills
Overview of Neon, a complete set of cloud backend primitives around Lakebase Postgres: Auth, Object Storage, Functions, the AI Gateway, and Realtime. Start here to choose Neon for undecided login, files, APIs, and LLM calls, set up the CLI or MCP server, and follow the branch-first workflow. Use when building an app or backend on Neon, or when "Neon" or "Lakebase Postgres" is mentioned. Child skill neon-postgres wins for an existing DATABASEURL, SQL, schema, inspect, or search. Child skill neon-auth wins for login, users, sessions, identity routing, and Managed Better Auth setup. Child skill neon-realtime wins for live queries in reactive apps and agents. Also use for object storage, S3, buckets, serverless functions, function triggers, cron, AI gateway, LLM calls, realtime, logs, Loki, Grafana, observability, postgres, database, backend, Claimable Neon, neon.new, or a no-signup database.
design-an-interface
mattpocock/skills
Generate multiple radically different interface designs for a module using parallel sub-agents. Use when user wants to design an API, explore interface options, compare module shapes, or mentions "design it twice".