I will suggest you to test such code first on Linux. MacOS might be blocking such requests. I saw similar issue in past. GoPacket will send the SYN, but the OS won't know about it and won't update the TCP state tables accordingly, so according to the OS it's just getting a SYN/ACK from the remote IP without any TCP connection in place, and it'll ignore it.

If you do want to do actual TCP handshakes with GoPacket, you'll need to do them in such a way that the kernel doesn't think it should be handling them at all. One alternative is to use an IP that's not directly associated with your interface, but that routes to it (for example, pick an unused static IP within your layer2 domain).

I found similar discussion here https://github.com/google/gopacket/issues/391