refactor: use WaitGroup.Go to replace wg.Add(1)/go/wg.Done() boilerplate (#222)

https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/modernize#hdr-Analyzer_waitgroup

pkg/client/dns.go

@@ -61,14 +61,11 @@ func (cli *Client) CreateIngressRecords(ctx context.Context, serviceID string) (
 			continue
 		}
 
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-
+		wg.Go(func() {
 			if err = verifyCaddyReachable(ctx, m.Machine); err == nil {
 				reachableMachines <- m.Machine
 			}
-		}()
+		})
 	}
 
 	go func() {

pkg/client/service.go

@@ -240,11 +240,7 @@ func (cli *Client) RemoveService(ctx context.Context, id string) error {
 
 	// Remove all containers on all machines that belong to the service.
 	for _, mc := range svc.Containers {
-		wg.Add(1)
-
-		go func() {
-			defer wg.Done()
-
+		wg.Go(func() {
 			err := cli.StopContainer(ctx, svc.ID, mc.Container.ID, container.StopOptions{})
 			if err != nil {
 				errCh <- fmt.Errorf("stop container '%s': %w", mc.Container.ID, err)
@@ -258,7 +254,7 @@ func (cli *Client) RemoveService(ctx context.Context, id string) error {
 			if err != nil && !errors.Is(err, api.ErrNotFound) {
 				errCh <- fmt.Errorf("remove container '%s': %w", mc.Container.ID, err)
 			}
-		}()
+		})
 	}
 
 	go func() {
@@ -286,16 +282,12 @@ func (cli *Client) StopService(ctx context.Context, id string, opts container.St
 
 	// Stop all containers on all machines that belong to the service.
 	for _, mc := range svc.Containers {
-		wg.Add(1)
-
-		go func() {
-			defer wg.Done()
-
+		wg.Go(func() {
 			err := cli.StopContainer(ctx, svc.ID, mc.Container.ID, opts)
 			if err != nil {
 				errCh <- fmt.Errorf("stop container '%s': %w", mc.Container.ID, err)
 			}
-		}()
+		})
 	}
 
 	go func() {
@@ -323,16 +315,12 @@ func (cli *Client) StartService(ctx context.Context, id string) error {
 
 	// Start all containers on all machines that belong to the service.
 	for _, mc := range svc.Containers {
-		wg.Add(1)
-
-		go func() {
-			defer wg.Done()
-
+		wg.Go(func() {
 			err := cli.StartContainer(ctx, svc.ID, mc.Container.ID)
 			if err != nil {
 				errCh <- fmt.Errorf("start container '%s': %w", mc.Container.ID, err)
 			}
-		}()
+		})
 	}
 
 	go func() {