JetBrains published go-modern-guidelines, an official skill teaching agents to stop writing outdated Go.

The repo (1,861 stars, +314 today) ships a SKILL.md covering useful features from Go 1.0 through 1.27, including everything the modernize analyzer targets, so agents use max(a, b) over if-else, slices.Contains over manual loops, and Go 1.26 additions like new(42) and errors.AsType[T] (GitHub). JetBrains names two causes explicitly: training-data lag for post-cutoff features, and frequency bias, where more for i := 0; i < n; i++ in training data outvotes for i := range n even when the model knows both. The agent detects the project's Go version from go.mod and restricts itself accordingly. Ships for Junie, Claude Code, Codex and Cursor.