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

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.