// Make sure panic during callback unwinds properly.
	if lockedOSThread() {
		t.Fatal("locked OS thread on entry to TestCallbackPanic")
	}
	defer func() {
		s := recover()
		if s == nil {
			t.Fatal("did not panic")
		}
		if s.(string) != "callback panic" {
			t.Fatal("wrong panic:", s)
		}
		if lockedOSThread() {
			t.Fatal("locked OS thread on exit from TestCallbackPanic")
		}
	}()

to define an interface called <code>Locker</code>:
</p>

<pre>
type Locker interface {
	Lock()
	Unlock()
}
</pre>

<p>
If <code>S1</code> and <code>S2</code> also implement
</p>

<pre>
func (p T) Lock() { … }
func (p T) Unlock() { … }
</pre>

<p>
they implement the <code>Locker</code> interface as well
as the <code>File</code> interface.

pkg sync, method (*WaitGroup) Done()
pkg sync, method (*WaitGroup) Wait()
pkg sync, type Cond struct
pkg sync, type Cond struct, L Locker
pkg sync, type Locker interface { Lock, Unlock }
pkg sync, type Locker interface, Lock()
pkg sync, type Locker interface, Unlock()
pkg sync, type Mutex struct
pkg sync, type Once struct
pkg sync, type RWMutex struct
pkg sync, type WaitGroup struct

pkg syscall (freebsd-arm64), const RTF_REJECT = 8
pkg syscall (freebsd-arm64), const RTF_REJECT ideal-int
pkg syscall (freebsd-arm64), const RTF_RNH_LOCKED = 1073741824
pkg syscall (freebsd-arm64), const RTF_RNH_LOCKED ideal-int
pkg syscall (freebsd-arm64), const RTF_STATIC = 2048
pkg syscall (freebsd-arm64), const RTF_STATIC ideal-int
pkg syscall (freebsd-arm64), const RTF_STICKY = 268435456

pkg syscall (windows-386), const SidTypeWellKnownGroup = 5
pkg syscall (windows-386), const TF_DISCONNECT = 1
pkg syscall (windows-386), const TF_REUSE_SOCKET = 2
pkg syscall (windows-386), const TF_USE_DEFAULT_WORKER = 0
pkg syscall (windows-386), const TF_USE_KERNEL_APC = 32
pkg syscall (windows-386), const TF_USE_SYSTEM_THREAD = 16
pkg syscall (windows-386), const TF_WRITE_BEHIND = 4

to define an interface called <code>Locker</code>:
</p>

<pre>
type Locker interface {
	Lock()
	Unlock()
}
</pre>

<p>
If <code>S1</code> and <code>S2</code> also implement
</p>

<pre>
func (p T) Lock() { … }
func (p T) Unlock() { … }
</pre>

<p>
they implement the <code>Locker</code> interface as well
as the <code>File</code> interface.

		for {
			select {
			case <-stop:
				return
			case <-time.After(time.Millisecond * 100):
			}
		}
	}()
	defer close(stop)

	for i := 0; i < 1000; i++ {
		if !C.Ctid() {
			t.Fatalf("cgo has not locked OS thread")
		}
	}

pkg syscall (freebsd-386-cgo), const RTF_PROTO2 ideal-int
pkg syscall (freebsd-386-cgo), const RTF_PROTO3 ideal-int
pkg syscall (freebsd-386-cgo), const RTF_REJECT ideal-int
pkg syscall (freebsd-386-cgo), const RTF_RNH_LOCKED ideal-int
pkg syscall (freebsd-386-cgo), const RTF_STATIC ideal-int
pkg syscall (freebsd-386-cgo), const RTF_STICKY ideal-int
pkg syscall (freebsd-386-cgo), const RTF_UP ideal-int

pkg syscall (freebsd-riscv64), const RTF_REJECT = 8 #53466
pkg syscall (freebsd-riscv64), const RTF_REJECT ideal-int #53466
pkg syscall (freebsd-riscv64), const RTF_RNH_LOCKED = 1073741824 #53466
pkg syscall (freebsd-riscv64), const RTF_RNH_LOCKED ideal-int #53466
pkg syscall (freebsd-riscv64), const RTF_STATIC = 2048 #53466
pkg syscall (freebsd-riscv64), const RTF_STATIC ideal-int #53466