sns

// Create the SNS API with the required config, credentials, etc.
customResolver := aws.EndpointResolverWithOptionsFunc(func(service, region string, options ...interface{}) (aws.Endpoint, error) {
	if service == sns.ServiceID && region == "eu-west-1" {
		return aws.Endpoint{
			URL:           "http://localhost:4575",
			SigningRegion: "eu-west-1",
		}, nil
	}
	// returning EndpointNotFoundError will allow the service to fallback to it's default resolution
	return aws.Endpoint{}, &aws.EndpointNotFoundError{}
})

cfg, err := config.LoadDefaultConfig(context.TODO(),
	config.WithRegion("eu-west-1"),
	config.WithEndpointResolverWithOptions(customResolver),
	config.WithCredentialsProvider(aws.NewCredentialsCache(credentials.NewStaticCredentialsProvider("aws-id", "aws-secret", "aws-token"))),
)
if err != nil {
	log.Fatal(err)
}

api := sns.NewFromConfig(cfg)

// Create the publisher
pub, err := New(api)
if err != nil {
	log.Fatal(err)
}

input := &sns.PublishInput{
	Message:   aws.String("my message"),
	TargetArn: nil, TopicArn: aws.String("arn:aws:sns:eu-west-1:123456789012:MyTopic"),
}

// Publish it
msgID, err := pub.Publish(context.Background(), input)
if err != nil {
	log.Fatal(err)
}

fmt.Println(msgID)