net: add missing File method document
R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/8698049
diff --git a/src/pkg/net/unixsock_plan9.go b/src/pkg/net/unixsock_plan9.go
index 0390207..8a1281f 100644
--- a/src/pkg/net/unixsock_plan9.go
+++ b/src/pkg/net/unixsock_plan9.go
@@ -126,6 +126,10 @@
// 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 l does not affect f, and closing f does not affect l.
+//
+// The returned os.File's file descriptor is different from the
+// connection's. Attempting to change properties of the original
+// using this duplicate may or may not have the desired effect.
func (l *UnixListener) File() (*os.File, error) {
return nil, syscall.EPLAN9
}
