Fix server goroutine leak in forwardRequest: add handshake deadline

forwardRequest opens a stream to the destination and reads the
response. If the destination accepts but never responds, readObject
blocks forever — observed as 2.4K+ stuck goroutines per server,
growing rapidly after restart.

The idle timeout fix (PR skycoin#372) only covered the bridge phase
(CopyReadWriteCloser). This adds HandshakeTimeout to the
forwardRequest handshake read, matching the client-side behavior.

Author: 0pcom

pkg/dmsg/server_session.go

@@ -366,12 +366,22 @@ func (ss *ServerSession) forwardRequest(req StreamRequest) (mStr io.ReadWriteClo
 			return nil, nil, err
 		}
 	}
+	// Set a deadline for the forwarding handshake. If the destination visor
+	// accepts the stream but never responds, readObject blocks forever,
+	// leaking goroutines. Observed as 2K+ stuck goroutines per DMSG server.
+	if conn, ok := mStr.(net.Conn); ok {
+		conn.SetDeadline(time.Now().Add(HandshakeTimeout)) //nolint:errcheck,gosec
+	}
 	if err = ss.writeObject(mStr, req.raw); err != nil {
 		return nil, nil, err
 	}
 	if respObj, err = ss.readObject(mStr); err != nil {
 		return nil, nil, err
 	}
+	// Clear deadline before returning the stream for long-lived bridging.
+	if conn, ok := mStr.(net.Conn); ok {
+		conn.SetDeadline(time.Time{}) //nolint:errcheck,gosec
+	}
 	var resp StreamResponse
 	if resp, err = respObj.ObtainStreamResponse(); err != nil {
 		return nil, nil, err