net: fix documentation for SetLinger

Fixes #7974.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/95320043

src/pkg/net/tcpsock_plan9.go

@@ -44,17 +44,18 @@ func (c *TCPConn) CloseWrite() error {
 	return c.fd.closeWrite()
 }
 
-// SetLinger sets the behavior of Close() on a connection which still
+// SetLinger sets the behavior of Close on a connection which still
 // has data waiting to be sent or to be acknowledged.
 //
-// If sec < 0 (the default), Close returns immediately and the
-// operating system finishes sending the data in the background.
+// If sec < 0 (the default), the operating system finishes sending the
+// data in the background.
 //
-// If sec == 0, Close returns immediately and the operating system
-// discards any unsent or unacknowledged data.
+// If sec == 0, the operating system discards any unsent or
+// unacknowledged data.
 //
-// If sec > 0, Close blocks for at most sec seconds waiting for data
-// to be sent and acknowledged.
+// If sec > 0, the data is sent in the background as with sec < 0. On
+// some operating systems after sec seconds have elapsed any remaining
+// unsent data may be discarded.
 func (c *TCPConn) SetLinger(sec int) error {
 	return syscall.EPLAN9
 }

src/pkg/net/tcpsock_posix.go

@@ -90,17 +90,18 @@ func (c *TCPConn) CloseWrite() error {
 	return c.fd.closeWrite()
 }
 
-// SetLinger sets the behavior of Close() on a connection which still
+// SetLinger sets the behavior of Close on a connection which still
 // has data waiting to be sent or to be acknowledged.
 //
-// If sec < 0 (the default), Close returns immediately and the
-// operating system finishes sending the data in the background.
+// If sec < 0 (the default), the operating system finishes sending the
+// data in the background.
 //
-// If sec == 0, Close returns immediately and the operating system
-// discards any unsent or unacknowledged data.
+// If sec == 0, the operating system discards any unsent or
+// unacknowledged data.
 //
-// If sec > 0, Close blocks for at most sec seconds waiting for data
-// to be sent and acknowledged.
+// If sec > 0, the data is sent in the background as with sec < 0. On
+// some operating systems after sec seconds have elapsed any remaining
+// unsent data may be discarded.
 func (c *TCPConn) SetLinger(sec int) error {
 	if !c.ok() {
 		return syscall.EINVAL