Modern Go Guidelines

Modern Go Guidelines is an official JetBrains open-source project that provides structured guidelines for AI coding agents, helping them produce idiomatic, up-to-date Go code. It is licensed under Apache 2.0 and available freely on GitHub. The project addresses a well-documented problem: coding agents tend to generate outdated Go patterns due to training data lag and frequency bias toward older idioms.

What It Is

Modern Go Guidelines is a skill package — a curated reference document and CLI wrapper — that agents can load to understand Go language features from version 1.0 through 1.27. Rather than a standalone IDE or editor, it is a plugin/skill that integrates into existing AI coding agents such as Junie, Claude Code, Codex, Cursor, and others via skills.sh. When active, the agent automatically detects the project's Go version from go.mod and applies only the features available up to that version.

Why It Exists: The Outdated Go Problem

The README identifies two root causes for agents generating stale Go code:

• Training data lag: Models cannot use features added after their training cutoff. For example, errors.AsType[T] (Go 1.26) is unknown to models trained before that release.
• Frequency bias: Even for known features, models default to older patterns because older idioms appear more frequently in training data — e.g., for i := 0; i < n; i++ over for i := range n.

The guidelines fix both by giving the agent an explicit, versioned reference. This aligns with the Go team's own modernize analyzer, which automatically updates existing code to newer idioms. Modern Go Guidelines serves the same goal for new code: agents write modern Go from the start.

Concrete Examples of What It Changes

With these guidelines loaded, an agent will:

• Use max(a, b) instead of an if-else block
• Use slices.Contains instead of a manual loop
• Use cmp.Or(a, b, c) instead of a chain of nil checks
• Use new(42) to get a pointer to a value (Go 1.26)
• Use errors.AsType[T](err) for type-safe error matching (Go 1.26)

Supported Agents and Setup Path

The guidelines are distributed as installable plugins or skills for multiple agents:

• Junie (JetBrains' own agent): install via /extensions marketplace add inside a Junie CLI session
• Claude Code: install via /plugin marketplace add and /plugin install
• Codex: install via codex plugin marketplace add and codex plugin add
• Cursor: install via cursor-agent plugin marketplace add and the /plugins command
• Other agents (e.g., OpenCode): install via npx skills add JetBrains/go-modern-guidelines

All marketplace integrations run a small CLI installed on first use via go install. The Go toolchain must be present on PATH. The CLI targets Go 1.25 or newer but works on older versions when GOTOOLCHAIN=auto is set (the default), allowing Go to fetch a compatible toolchain automatically.

Open-Source Deployment Model

The project is fully open source under Apache License 2.0. The CLI is installed into a local cache (e.g., ~/.cache/go-modern-guidelines) and never modifies the user's project. A local development mode (GO_MODERN_GUIDELINES_DEV=1) lets contributors test changes to the CLI across all supported agents without releasing a new version. The repository had 2,477 stars and 75 forks as of its last recorded metadata, indicating meaningful community interest for a developer tooling project.