An example of tcp and gzip in golang.

tcp-gzip.go

package main

import (
	"compress/gzip"
	"io"
	"log"
	"net"
)

func main() {
	l, err := net.Listen("tcp", ":5000")
	if err != nil {
		log.Fatal(err)
	}
	for {
		conn, err := l.Accept()
		if err != nil {
			log.Fatal(err)
		}
		go func(c net.Conn) {
			defer c.Close()
			r, w := io.Pipe()
			go func() {
				defer w.Close()
				gzr, err := gzip.NewReader(c)
				if err != nil {
					log.Fatal(err)
				}
				io.Copy(w, gzr)
			}()
			io.Copy(c, r)
		}(conn)
	}
}

test.sh

#!/bin/bash
set -eu

rm -f hello.txt hello.txt.gz

# start server
go run tcp-gzip.go &

# send gzip data
echo "Hello, tcp!" > hello.txt
gzip hello.txt
nc localhost 5000 < hello.txt.gz

kill %%

Why not just

package main

import (
	"compress/gzip"
	"io"
	"log"
	"net"
)

func main() {
	l, err := net.Listen("tcp", ":5000")
	if err != nil {
		log.Fatal(err)
	}
	for {
		conn, err := l.Accept()
		if err != nil {
			log.Fatal(err)
		}
		go func(c net.Conn) {
			defer c.Close()
			gzr, _ := gzip.NewReader(c)
			io.Copy(c, gzr)
		}(conn)
	}
}

?

Though I don't remember what I wanted to do, maybe it was intended to manipulate the stream more after gzip, I think.