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 io/fs, var ErrClosed error
pkg io/fs, var ErrExist error
pkg io/fs, var ErrInvalid error
pkg io/fs, var ErrNotExist error
pkg io/fs, var ErrPermission error
pkg io/fs, var SkipDir error
pkg log, func Default() *Logger
pkg net, var ErrClosed error
pkg net/http, func FS(fs.FS) FileSystem
pkg net/http, type Transport struct, GetProxyConnectHeader func(context.Context, *url.URL, string) (Header, error)
pkg os, const ModeAppend fs.FileMode

pkg log/syslog (netbsd-arm64-cgo), const LOG_WARNING Priority
pkg log/syslog (netbsd-arm64-cgo), func Dial(string, string, Priority, string) (*Writer, error)
pkg log/syslog (netbsd-arm64-cgo), func NewLogger(Priority, int) (*log.Logger, error)
pkg log/syslog (netbsd-arm64-cgo), func New(Priority, string) (*Writer, error)
pkg log/syslog (netbsd-arm64-cgo), method (*Writer) Alert(string) error
pkg log/syslog (netbsd-arm64-cgo), method (*Writer) Close() error