inmem: Sender implements Close

Signed-off-by: Solomon Hykes <solomon@docker.com>

inmem/inmem.go

@@ -8,6 +8,7 @@ import (
 
 type Sender interface {
 	Send(msg *Message, mode int) (Receiver, Sender, error)
+	Close() error
 }
 
 type Receiver interface {

inmem/nop.go

@@ -10,6 +10,10 @@ func (s NopSender) Send(msg *Message, mode int) (Receiver, Sender, error) {
 	return NopReceiver{}, NopSender{}, nil
 }
 
+func (s NopSender) Close() error {
+	return nil
+}
+
 type NopReceiver struct{}
 
 func (r NopReceiver) Receive(mode int) (*Message, Receiver, Sender, error) {