Compilers do not restructure a causal chain of events between a client and server in a different process. It's very easy to understand this when you realize that send -> wait for response and read it will result in certain system calls, no matter the language.
[Send 4 bytes * 200, then (round trip latency later) receive 4 bytes * 200] is fundamentally different than [(send 4 bytes, then (round trip latency later) receive 4 bytes) * 200]. Whether the message content is "ignored" is irrelevant.
Or, put another way, it's ridiculous for you to modify the Go program in that way (which will very likely send and receive only a single TCP segment over the localhost "network") and report the faster time as if it means anything. If you modify both programs in that way, fine. But it's something completely different.
[Send 4 bytes * 200, then (round trip latency later) receive 4 bytes * 200] is fundamentally different than [(send 4 bytes, then (round trip latency later) receive 4 bytes) * 200]. Whether the message content is "ignored" is irrelevant.
Or, put another way, it's ridiculous for you to modify the Go program in that way (which will very likely send and receive only a single TCP segment over the localhost "network") and report the faster time as if it means anything. If you modify both programs in that way, fine. But it's something completely different.