go-modernize

Run a full scan that checks deprecated packages, language features like range-over-int and iterators, and standard library upgrades such as slices, maps, and slog. Suggestions are prioritized with safety fixes first, and the golangci-lint modernize linter automates detection.

math/rand/v2 replaces math/rand starting in Go 1.22. It removes the need for rand.Seed, renames Intn to IntN, adds generic functions like rand.N[T], and uses better algorithms such as ChaCha8 and PCG.

Yes, Go 1.22 gives each loop iteration a new variable, so shadow copies like v := v inside loops can be removed. The go directive in go.mod must be set to go 1.22 or later for this behavior to apply.

Yes, explicitly ignored suggestions are appended to a .modernize file in the project root with the date, category, and description. Every scan reads this file first and excludes all listed items from its output.

The guidance covers Go 1.21 through Go 1.26, released between 2023 and 2026, plus a few older still-missed improvements like any and errors.Is. Projects on Go 1.20 or earlier should upgrade their Go version first.

For new projects, prefer the standard library log/slog introduced in Go 1.21. For existing projects heavily invested in zap or logrus, migration is optional and ranked as a lower-priority gradual improvement.