The following steps cover writing and running your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter11/orchestrate and navigate to it.
2. Run the following command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter11/orchestrate

You should see a file called go.mod that contains the following content:

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter11/orchestrate    

3. Copy the tests from ~/projects/go-programming-cookbook-original/chapter11/orchestrate, or use this as an opportunity to write some of your own code!
4. Create a file called Dockerfile with the following content:

FROM golang:1.12.4-alpine3.9

ENV GOPATH /code/
ADD . /code/src/github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter11/docker
WORKDIR /code/src/github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter11/docker/example
RUN GO111MODULE=on GOPROXY=off go build -mod=vendor

ENTRYPOINT /code/src/github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter11/docker/example/example

5. Create a file called docker-compose.yml with the following content:

        version: '2'
        services:
         app:
         build: .
         mongodb:
         image: "mongo:latest"

6. Create a file called config.go with the following content:

package mongodb

import (
  "context"
  "fmt"
  "time"

  "github.com/mongodb/mongo-go-driver/mongo"
  "go.mongodb.org/mongo-driver/mongo/options"
)

// Setup initializes a mongo client
func Setup(ctx context.Context, address string) (*mongo.Client, error) {
  ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
  defer cancel()

  fmt.Println(address)
  client, err := mongo.NewClient(options.Client().ApplyURI(address))
  if err != nil {
    return nil, err
  }

  if err := client.Connect(ctx); err != nil {
    return nil, err
  }
  return client, nil
}

7. Create a file called exec.go with the following content:

package mongodb

import (
  "context"
  "fmt"

  "github.com/mongodb/mongo-go-driver/bson"
)

// State is our data model
type State struct {
  Name string `bson:"name"`
  Population int `bson:"pop"`
}

// Exec creates then queries an Example
func Exec(address string) error {
  ctx := context.Background()
  db, err := Setup(ctx, address)
  if err != nil {
    return err
  }

  conn := db.Database("gocookbook").Collection("example")

  vals := []interface{}{&State{"Washington", 7062000}, &State{"Oregon", 3970000}}

  // we can inserts many rows at once
  if _, err := conn.InsertMany(ctx, vals); err != nil {
    return err
  }

  var s State
  if err := conn.FindOne(ctx, bson.M{"name": "Washington"}).Decode(&s); err != nil {
    return err
  }

  if err := conn.Drop(ctx); err != nil {
    return err
  }

  fmt.Printf("State: %#v
", s)
  return nil
}

8. Create a new directory named example and navigate to it.
9. Create a main.go file with the following content:

package main

import mongodb "github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter11/orchestrate"

func main() {
  if err := mongodb.Exec("mongodb://mongodb:27017"); err != nil {
    panic(err)
  }
}

10. Navigate back to the starting directory.
11. Run the go mod vendor command.
12. Run the docker-compose up -d command.
13. Run the docker logs orchestrate_app_1 command. You should now see the following output:

$ docker logs orchestrate_app_1
State: docker.State{Name:"Washington", Population:7062000}

14. The go.mod file may be updated and the go.sum file should now be present in the top-level recipe directory.
15. If you copied or wrote your own tests, go up one directory and run go test. Ensure that all the tests pass.