go.mod: update toolchain base to 1.22

- Use math/rand/v2 where useful.
- Remove the "shuffled" helper from the tests.

example_test.go

@@ -6,7 +6,7 @@ import (
  "fmt"
  "io"
  "log"
- "math/rand"
+ "math/rand/v2"
  "strings"
  "time"
 
@@ -106,17 +106,6 @@ func ExampleGroup_Limit() {
  // Max active ≤ 4: true
 }
 
-func shuffled(n int) []int {
- vs := make([]int, n)
- for i := range vs {
- vs[i] = i + 1
- }
- rand.Shuffle(n, func(i, j int) {
- vs[i], vs[j] = vs[j], vs[i]
- })
- return vs
-}
-
 type slowReader struct {
  n int
  d time.Duration
@@ -171,7 +160,7 @@ func ExampleCollector() {
  })
 
  const numTasks = 25
- input := shuffled(500)
+ input := rand.Perm(500)
 
  // Start a bunch of tasks to find elements in the input...
  g := taskgroup.New(nil)

go.mod

@@ -1,5 +1,5 @@
 module github.com/creachadair/taskgroup
 
-go 1.21
+go 1.22
 
 require github.com/fortytw2/leaktest v1.3.0

taskgroup_test.go

@@ -3,7 +3,7 @@ package taskgroup_test
 import (
  "context"
  "errors"
- "math/rand"
+ "math/rand/v2"
  "reflect"
  "sync"
  "sync/atomic"
@@ -17,7 +17,7 @@ import (
 const numTasks = 64
 
 // randms returns a random duration of up to n milliseconds.
-func randms(n int) time.Duration { return time.Duration(rand.Intn(n)) * time.Millisecond }
+func randms(n int) time.Duration { return time.Duration(rand.IntN(n)) * time.Millisecond }
 
 // busyWork returns a Task that does nothing for n ms and returns err.
 func busyWork(n int, err error) taskgroup.Task {
@@ -265,7 +265,7 @@ func TestCollector(t *testing.T) {
  var sum int
  c := taskgroup.NewCollector(func(v int) { sum += v })
 
- vs := shuffled(15)
+ vs := rand.Perm(15)
  g := taskgroup.New(nil)
 
  for i, v := range vs {
@@ -295,7 +295,7 @@ func TestCollector_Report(t *testing.T) {
  c := taskgroup.NewCollector(func(v int) { sum += v })
 
  g := taskgroup.New(nil).Go(c.Report(func(report func(v int)) error {
- for _, v := range shuffled(10) {
+ for _, v := range rand.Perm(10) {
  report(v)
  }
  return nil
@@ -304,7 +304,7 @@ func TestCollector_Report(t *testing.T) {
  if err := g.Wait(); err != nil {
  t.Errorf("Unexpected error from group: %v", err)
  }
- if want := (10 * 11) / 2; sum != want {
+ if want := (9 * 10) / 2; sum != want {
  t.Errorf("Final result: got %d, want %d", sum, want)
  }
 }