go-idioms

Modernize Go code by first checking the go directive in go.mod, then replacing legacy patterns with std equivalents available at that version, such as sort.Slice with slices.Sort (1.21) or interface{} with any (1.18). APIs introduced after the directive version must be treated as upgrade-gated options.

io/ioutil functions map to os and io equivalents, deprecated since Go 1.16. Other deprecations include httputil.ReverseProxy.Director replaced by Rewrite in 1.26, and crypto/rsa PKCS #1 v1.5 encryption replaced by OAEP.

Yes, the go directive gates which language features and stdlib APIs apply to a module. You must never use an API introduced strictly after the directive version, though APIs introduced exactly at that version are available.

In a go.work workspace, resolve the go directive of the specific module that owns the file being edited, not the workspace file. Each module's directive independently gates which recommendations apply to its code.

Replace math/rand with math/rand/v2 when the go directive is 1.22 or higher, gaining rand.N and rand.IntN without seeding. Preserve the existing generator when callers depend on its exact historical output sequence, since v2 changes output streams.

Go 1.24 adds b.Loop() for benchmarks, t.Context() for test cancellation, and t.Chdir for directory changes. Go 1.25 adds testing/synctest for concurrency tests, and 1.26 adds T.ArtifactDir for test outputs.