Embed NATS in Go

main.go

package main

import (
	"flag"
	"log"

	"github.com/nats-io/nats-server/v2/server"
	nats "github.com/nats-io/nats.go"
)

func main() {

	// Declare CLI Flags
	embedNats := flag.Bool("embed-nats", true, "Start NATS as an embedded server")
	natsIPC := flag.Bool("nats-ipc", true, "Disable network interface for embedded NATS server and connect over inter-process communication (IPC).")

	// Parse CLI flags
	flag.Parse()

	var nc *nats.Conn
	var ns *server.Server
	var err error

	if *embedNats {
		// Start NATS embedded server
		nc, ns, err = core.EmbedNats(core.NatsOpts{
			ServerName:      "embeded-nats",
			ClientName:      "embedded-nats-client",
			JetStream:       true,
			JetStreamDomain: "example",
			IPC:             *natsIPC,
			Logging:         true,
		})
		defer ns.WaitForShutdown()

		if err != nil {
			log.Fatal(err)
		}
	}

	nc.Subscribe("u.system.test", func(m *nats.Msg) {
		m.Respond([]byte("Hi there!"))
	})
}

nats.go

package core

import (
	"time"

	server "github.com/nats-io/nats-server/v2/server"
	nats "github.com/nats-io/nats.go"
)

// Configuration options for NATS server and conn
type NatsOpts struct {
	// Name of the NATS server
	ServerName string
	// Name of the client for NATS
	ClientName string
	// Enable JetStream
	JetStream bool
	// Jetstream domain, e.g., "upspeak"
	JetStreamDomain string
	// Connect to NATS Server through Inter-Process Communication
	IPC bool
	// Enable logging for the embedded nats server
	Logging bool
}

// Start an embedded NATS server and create a NATS client
// See: https://www.youtube.com/watch?v=cdTrl8UfcBo
func EmbedNats(opts NatsOpts) (*nats.Conn, *server.Server, error) {
	serverOpts := &server.Options{
		ServerName:      opts.ServerName,
		DontListen:      opts.IPC,
		JetStream:       opts.JetStream,
		JetStreamDomain: opts.JetStreamDomain,
	}

	ns, err := server.NewServer(serverOpts)

	if err != nil {
		return nil, nil, err
	}

	if opts.Logging {
		ns.ConfigureLogger()
	}

	ns.Start()
	if !ns.ReadyForConnections(5 * time.Second) {
		return nil, nil, nats.ErrTimeout
	}

	clientOpts := []nats.Option{
		nats.Name(opts.ClientName),
	}
	if opts.IPC {
		clientOpts = append(clientOpts, nats.InProcessServer(ns))
	}
	nc, err := nats.Connect(nats.DefaultURL, clientOpts...)
	if err != nil {
		return nil, nil, err
	}

	return nc, ns, nil

}