Make Close() idempotent and close connection if session fails to close

muxconn/muxconn.go

@@ -16,6 +16,7 @@ var _ drpc.Conn = &Conn{}
 type Conn struct {
 	conn     io.ReadWriteCloser
 	sess     *yamux.Session
+	isClosed bool
 	closed   chan struct{}
 }
 
@@ -36,14 +37,19 @@ func New(conn io.ReadWriteCloser) (*Conn, error) {
 // Close closes the multiplexer session
 // and the underlying connection.
 func (m *Conn) Close() error {
+	if !m.isClosed {
+		m.isClosed = true
 		defer close(m.closed)
 
 		err := m.sess.Close()
 		if err != nil {
+			m.conn.Close()
 			return err
 		}
 		return m.conn.Close()
 	}
+	return nil
+}
 
 // Closed returns a channel that will be closed
 // when the connection is closed