chore: build with Go 1.26; use Go 1.25 features (#10570)

WaitGroup.Go and built-in gomaxprocs handling.

Signed-off-by: Jakob Borg <jakob@kastelo.net>

lib/syncutil/timeoutcond_test.go

@@ -48,16 +48,13 @@ func TestTimeoutCond(t *testing.T) {
 	var results [routines][2]int
 	var wg sync.WaitGroup
 	for i := 0; i < routines; i++ {
-		i := i
-		wg.Add(1)
-		go func() {
+		wg.Go(func() {
 			d := time.Duration(i) * timeMult * time.Millisecond
 			t.Logf("Routine %d waits for %v\n", i, d)
 			succ, fail := runLocks(t, iterations, c, d)
 			results[i][0] = succ
 			results[i][1] = fail
-			wg.Done()
-		}()
+		})
 	}
 
 	wg.Wait()