net: fix typo in Listener.File() documentation

R=golang-dev, dave, rsc
CC=golang-dev, remy
https://golang.org/cl/6097044

src/pkg/net/tcpsock_posix.go

@@ -357,5 +357,5 @@ func (l *TCPListener) SetDeadline(t time.Time) error {
 
 // File returns a copy of the underlying os.File, set to blocking mode.
 // It is the caller's responsibility to close f when finished.
-// Closing c does not affect f, and closing f does not affect c.
+// Closing l does not affect f, and closing f does not affect l.
 func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }

src/pkg/net/unixsock_posix.go

@@ -404,7 +404,7 @@ func (l *UnixListener) SetDeadline(t time.Time) (err error) {
 
 // File returns a copy of the underlying os.File, set to blocking mode.
 // It is the caller's responsibility to close f when finished.
-// Closing c does not affect f, and closing f does not affect c.
+// Closing l does not affect f, and closing f does not affect l.
 func (l *UnixListener) File() (f *os.File, err error) { return l.fd.dup() }
 
 // ListenUnixgram listens for incoming Unix datagram packets addressed to the