<p class="rule">
The completion of a single call of <code>f()</code> from <code>once.Do(f)</code>
is synchronized before the return of any call of <code>once.Do(f)</code>.
</p>

<p>
In this program:
</p>

<pre>
var a string
var once sync.Once

func setup() {
	a = "hello, world"
}

func doprint() {
	once.Do(setup)
	print(a)
}

func twoprint() {
	go doprint()

			// Retry only for the first retryable error.
			if osIsNotExist(err) && i == 0 {
				i++
				// Determine if os.NotExist error is because of
				// baseDir's parent being present, retry it once such
				// that the MkdirAll is retried once for the parent
				// of dirPath.
				// Because it is worth a retry to skip a different
				// baseDir which is slightly higher up the depth.
				nbaseDir := path.Dir(baseDir)

	"errors"
	"fmt"
	"net/url"
	"os"
	"path/filepath"

	"github.com/nsqio/go-nsq"

	"github.com/minio/minio/internal/event"
	"github.com/minio/minio/internal/logger"
	"github.com/minio/minio/internal/once"
	"github.com/minio/minio/internal/store"
	xnet "github.com/minio/pkg/v3/net"
)

// NSQ constants
const (
	NSQAddress       = "nsqd_address"
	NSQTopic         = "topic"
	NSQTLS           = "tls"

  - If you work for a company that wants to allow you to contribute your work,
    then you'll need to sign a [corporate CLA][].

You generally only need to submit a CLA once, so if you've already submitted
one (even if it was for a different project), you probably don't need to do it
again.

[individual CLA]: https://cla.developers.google.com/about/google-individual

/// tip

You normally have to do this only **once**, when you create the virtual environment.

///

## Deactivate the Virtual Environment { #deactivate-the-virtual-environment }

Once you are done working on your project you can **deactivate** the virtual environment.

<div class="termy">

```console
$ deactivate
```

 * therefore every method of the listener will be called at most once. N.B. The {@link State#FAILED}
 * and {@link State#TERMINATED} states are terminal states, once a service enters either of these
 * states it cannot ever leave them.
 *
 * <p>Implementors of this interface are strongly encouraged to extend one of the abstract classes

	ARCH=$(uname -m)
	case "${KNAME}" in
	SunOS)
		ARCH=$(isainfo -k)
		;;
	esac
}

## FIXME:
## In OSX, 'readlink -f' option does not exist, hence
## we have our own readlink -f behavior here.
## Once OSX has the option, below function is good enough.
##
## readlink() {
##     return /bin/readlink -f "$1"
## }
##
readlink() {
	TARGET_FILE=$1

	cd $(dirname $TARGET_FILE)

/// tip | İpucu

Sonraki bölümler **mutlaka "gelişmiş" olmak zorunda değildir**.

Kullanım şeklinize bağlı olarak, çözümünüz bu bölümlerden birinde olabilir.

///

## Önce Öğreticiyi Okuyun

Sonraki bölümler [Tutorial - User Guide: Security](../../tutorial/security/index.md){.internal-link target=_blank} sayfasını okuduğunuzu varsayarak hazırlanmıştır.

// freezeServices will freeze all incoming S3 API calls.
// For each call, unfreezeServices must be called once.
func freezeServices() {
	// Use atomics for globalServiceFreeze, so we can read without locking.
	// We need a lock since we are need the 2 atomic values to remain in sync.
	globalServiceFreezeMu.Lock()
	// If multiple calls, first one creates channel.
	globalServiceFreezeCnt++
	if globalServiceFreezeCnt == 1 {

    return a == b || (a != null && a.equals(b));
  }

  // This one-liner saves us from some ugly casts
  protected Entry<K, V> entry(K key, V value) {
    return mapEntry(key, value);
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    // TODO: move this to invariant checks once the appropriate hook exists?
    super.expectContents(expected);