package once

// Singleton contains a pointer to T that must be set once.
// Until the value is set all Get() calls will block.
type Singleton[T any] struct {
	v   *T
	set chan struct{}
}

// NewSingleton creates a new unset singleton.
func NewSingleton[T any]() *Singleton[T] {
	return &Singleton[T]{set: make(chan struct{}), v: nil}
}

// Get will return the singleton value.
func (s *Singleton[T]) Get() *T {
	<-s.set
	return s.v

    assertEquals(0, (int) iter.peek());
    assertEquals(0, (int) iter.next());

    assertEquals(1, (int) iter.peek());
    assertEquals(1, (int) iter.next());

    /*
     * We test peek() after various calls to make sure that one bad call doesn't interfere with its
     * ability to throw the correct exception in the future.
     */
    assertThrows(NoSuchElementException.class, iter::peek);

    assertEquals(0, (int) iter.peek());
    assertEquals(0, (int) iter.next());

    assertEquals(1, (int) iter.peek());
    assertEquals(1, (int) iter.next());

    /*
     * We test peek() after various calls to make sure that one bad call doesn't interfere with its
     * ability to throw the correct exception in the future.
     */
    assertThrows(NoSuchElementException.class, iter::peek);

    certain bad routes indefinitely; now we only track the ones that could be necessary.
 *  Fix: Defer proxy selection until a proxy is required. This saves calls to `ProxySelector` on
    calls that use a pooled connection.


## Version 4.3.1

_2020-01-07_

 *  Fix: Don't crash with a `NullPointerException` when a web socket is closed before it connects.

import java.util.NoSuchElementException;
import java.util.Queue;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A queue which forwards all its method calls to another queue. Subclasses should override one or
 * more methods to modify the behavior of the backing queue as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

import java.util.Collection;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A set which forwards all its method calls to another set. Subclasses should override one or more
 * methods to modify the behavior of the backing set as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

///

## Other Asynchronous Function Calls

As the testing function is now asynchronous, you can now also call (and `await`) other `async` functions apart from sending requests to your FastAPI application in your tests, exactly as you would call them anywhere else in your code.

/// tip

import java.util.Collection;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.TimeUnit;
import javax.annotation.CheckForNull;

/**
 * A {@link BlockingDeque} which forwards all its method calls to another {@code BlockingDeque}.
 * Subclasses should override one or more methods to modify the behavior of the backing deque as
 * desired per the <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *

  *** getJavaLangAccess(...);
}
-dontnote sun.misc.JavaLangAccess
-keep class sun.misc.JavaLangAccess {
  *** getStackTraceElement(...);
  *** getStackTraceDepth(...);
}

# FinalizableReferenceQueue calls this reflectively
# Proguard is intelligent enough to spot the use of reflection onto this, so we
# only need to keep the names, and allow it to be stripped out if
# FinalizableReferenceQueue is unused.

     * immediately fails with the same exception:
     *
     * Thread1: calls setException(), which returns true, context switch before it can CAS
     * seenExceptions to its exception
     *
     * Thread2: calls setException(), which returns false, CASes seenExceptions to its exception,