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/connections/connections_test.go

@@ -337,23 +337,20 @@ func BenchmarkConnections(b *testing.B) {
 						b.ResetTimer()
 						for i := 0; i < b.N; i++ {
 							var wg sync.WaitGroup
-							wg.Add(2)
 							errC := make(chan error, 2)
-							go func() {
+							wg.Go(func() {
 								if _, err := client.Write(data); err != nil {
 									errC <- err
 									return
 								}
-								wg.Done()
-							}()
-							go func() {
+							})
+							wg.Go(func() {
 								if _, err := io.ReadFull(server, data); err != nil {
 									errC <- err
 									return
 								}
 								total += sz
-								wg.Done()
-							}()
+							})
 							wg.Wait()
 							close(errC)
 							err := <-errC