sub.go

package main

import (
        "context"
        "fmt"
        "github.com/nats-io/nats.go"
)

func main() {
        nc, err := nats.Connect("localhost")
	if err != nil {
		panic(err)
	}
	
	// Subscribe sets up go routines to handle the message and call the
	// function in the background and returns to your application for
	// other work
        nc.Subscribe("demo.hello", func(m *nats.Msg) {
                fmt.Printf("Received a message: %s\n", string(m.Data))
        })

	// this is like a super minimal app, so all we do is pause forever
	// letting the background stuff do their thing
        <-context.Background().Done()
}

z.txt

% go run sub.go
Received a message: test