main.go

package main

import (
	"io"
	"os/exec"

	"github.com/nats-io/nats.go"
)

type NWriter struct {
	nc *nats.Conn
}

func (nw *NWriter) Write(p []byte) (n int, err error) {
	err = nw.nc.Publish("updates", p)
	if err != nil {
		return 0, err
	}
	return len(p), nil
}

func main() {

	nc, err := nats.Connect("nats://localhost:4222")
	if err != nil {
		panic(err)
	}

	defer nc.Close()

	// echo
	cmd := exec.Command("cat", "-")

	in, _ := cmd.StdinPipe()
	out, _ := cmd.StdoutPipe()

	_, err = nc.Subscribe("in", func(m *nats.Msg) {
		in.Write(m.Data) // Write the received message to the command's stdin
		println("Received message:", string(m.Data))
	})
	if err != nil {
		panic(err)
	}

	nw := &NWriter{nc: nc}

	go func() {
		_, err := io.Copy(nw, out) // Copy data from stdout to nats
		if err != nil {
			println("Error copying data:", err.Error())
		}
	}()

	cmd.Start()
	if err := cmd.Wait(); err != nil {
		println("Command finished with error:", err.Error())
	}

}