How to do it...

These steps cover writing and running your application:

1. From your Terminal or console application, create a new directory called ~/projects/go-programming-cookbook/chapter6/mongodb and navigate to this directory.
2. Run the following command:

$ go mod init github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter6/mongodb

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

module github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter6/mongodb    

3. Copy tests from ~/projects/go-programming-cookbook-original/chapter6/mongodb, or use this as an exercise to write some code of your own!

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

package mongodb

import (
  "context"
  "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, 10*time.Second)
  // cancel will be called when setup exits
  defer cancel()

  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
}

5. 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
  }

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

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

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

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

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

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

6. Navigate to example.
7. Create a file called main.go with the following content:

package main

import "github.com/PacktPublishing/Go-Programming-Cookbook-Second-Edition/chapter6/mongodb"

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

8. Run go run main.go.
9. You could also run the following command:

$ go build
$ ./example

You should see the following output:

$ go run main.go
State: mongodb.State{Name:"Washington", Population:7062000}

10. The go.mod file may be updated and go.sum file should now be present in the top-level recipe directory.

11. If you copied or wrote your own tests, go up one directory and run go test. Ensure that all tests pass.