do not use atomic

provider/appconfig/appconfig.go

@@ -17,7 +17,6 @@ import (
 	"log/slog"
 	"reflect"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/aws/aws-sdk-go-v2/aws"
@@ -39,11 +38,11 @@ type AppConfig struct {
 	pollInterval time.Duration
 
 	timeout time.Duration
-	token   atomic.Pointer[string]
+	token   *string
 }
 
 // New creates an AppConfig with the given application, environment, profile and Option(s).
-func New(application, environment, profile string, opts ...Option) *AppConfig {
+func New(application, environment, profile string, opts ...Option) AppConfig {
 	if application == "" {
 		panic("cannot create AppConfig with empty application")
 	}
@@ -76,14 +75,14 @@ func New(application, environment, profile string, opts ...Option) *AppConfig {
 	}
 	option.client = &clientProxy{config: option.awsConfig}
 
-	return &option.AppConfig
+	return option.AppConfig
 }
 
-func (a *AppConfig) Load() (map[string]any, error) {
+func (a AppConfig) Load() (map[string]any, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), a.timeout)
 	defer cancel()
 
-	if a.token.Load() == nil {
+	if a.token == nil {
 		input := &appconfigdata.StartConfigurationSessionInput{
 			ApplicationIdentifier:                aws.String(a.application),
 			ConfigurationProfileIdentifier:       aws.String(a.profile),
@@ -94,20 +93,20 @@ func (a *AppConfig) Load() (map[string]any, error) {
 		if err != nil {
 			return nil, err
 		}
-		a.token.Store(output.InitialConfigurationToken)
+		a.token = output.InitialConfigurationToken
 	}
 
 	return a.load(ctx)
 }
 
-func (a *AppConfig) Watch(ctx context.Context, onChange func(map[string]any)) error {
+func (a AppConfig) Watch(ctx context.Context, onChange func(map[string]any)) error {
 	ticker := time.NewTicker(a.pollInterval)
 	defer ticker.Stop()
 
 	for {
 		select {
 		case <-ticker.C:
-			out, err := a.load(ctx)
+			values, err := a.load(ctx)
 			if err != nil {
 				a.logger.WarnContext(
 					ctx, "Error when reloading from AWS AppConfig",
@@ -120,27 +119,27 @@ func (a *AppConfig) Watch(ctx context.Context, onChange func(map[string]any)) er
 				continue
 			}
 
-			if out != nil {
-				onChange(out)
+			if values != nil {
+				onChange(values)
 			}
 		case <-ctx.Done():
 			return nil
 		}
 	}
 }
 
-func (a *AppConfig) load(ctx context.Context) (map[string]any, error) {
+func (a AppConfig) load(ctx context.Context) (map[string]any, error) {
 	ctx, cancel := context.WithTimeout(ctx, a.timeout)
 	defer cancel()
 
 	input := &appconfigdata.GetLatestConfigurationInput{
-		ConfigurationToken: a.token.Load(),
+		ConfigurationToken: a.token,
 	}
 	output, err := a.client.GetLatestConfiguration(ctx, input)
 	if err != nil {
 		return nil, err
 	}
-	a.token.Store(output.NextPollConfigurationToken)
+	a.token = output.NextPollConfigurationToken
 
 	if len(output.Configuration) == 0 {
 		// It may return empty configuration data
@@ -156,7 +155,7 @@ func (a *AppConfig) load(ctx context.Context) (map[string]any, error) {
 	return out, nil
 }
 
-func (a *AppConfig) String() string {
+func (a AppConfig) String() string {
 	return "appConfig:" + a.application + "-" + a.environment + "-" + a.profile
 }
 
@@ -208,16 +207,14 @@ func (c *clientProxy) loadClient(ctx context.Context) (*appconfigdata.Client, er
 	c.clientOnce.Do(func() {
 		if reflect.ValueOf(c.config).IsZero() {
 			if c.config, err = config.LoadDefaultConfig(ctx); err != nil {
+				err = fmt.Errorf("load default AWS config: %w", err)
+
 				return
 			}
 		}
 
 		c.client = appconfigdata.NewFromConfig(c.config)
 	})
 
-	if err != nil {
-		return nil, fmt.Errorf("load client: %w", err)
-	}
-
-	return c.client, nil
+	return c.client, err
 }

provider/appconfig/benchmark_test.go

@@ -18,7 +18,7 @@ import (
 )
 
 func BenchmarkNew(b *testing.B) {
-	var loader *appconfig.AppConfig
+	var loader appconfig.AppConfig
 	for i := 0; i < b.N; i++ {
 		loader = appconfig.New("app", "env", "profile")
 	}

provider/flag/option.go

@@ -42,7 +42,7 @@ func WithDelimiter(delimiter string) Option {
 	}
 }
 
-// WithNameSplitter provides the function used to split environment variable names into nested keys.
+// WithNameSplitter provides the function used to split flag names into nested keys.
 // If it returns an nil/[]string{}/[]string{""}, the variable will be ignored.
 //
 // For example, with the default splitter, an flag name like "parent.child.key"

provider/pflag/option.go

@@ -43,7 +43,7 @@ func WithDelimiter(delimiter string) Option {
 	}
 }
 
-// WithNameSplitter provides the function used to split environment variable names into nested keys.
+// WithNameSplitter provides the function used to split flag names into nested keys.
 // If it returns an nil/[]string{}/[]string{""}, the variable will be ignored.
 //
 // For example, with the default splitter, an flag name like "parent.child.key"