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/database and navigate to this directory.
2. Run the following command:

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

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

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

3. Copy tests from ~/projects/go-programming-cookbook-original/chapter6/database, 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 database

        import (
            "database/sql"
            "fmt"
            "os"
            "time"

            _ "github.com/go-sql-driver/mysql" //we import supported 
            libraries for database/sql
        )

        // Example hold the results of our queries
        type Example struct {
            Name string
            Created *time.Time
        }

        // Setup configures and returns our database
        // connection poold
        func Setup() (*sql.DB, error) {
            db, err := sql.Open("mysql", 
            fmt.Sprintf("%s:%s@/gocookbook? 
            parseTime=true", os.Getenv("MYSQLUSERNAME"), 
            os.Getenv("MYSQLPASSWORD")))
            if err != nil {
                return nil, err
            }
            return db, nil
        }

5. Create a file called create.go with the following content:

        package database

        import (
            "database/sql"

            _ "github.com/go-sql-driver/mysql" //we import supported 
            libraries for database/sql
        )

        // Create makes a table called example
        // and populates it
        func Create(db *sql.DB) error {
            // create the database
            if _, err := db.Exec("CREATE TABLE example (name 
            VARCHAR(20), created DATETIME)"); err != nil {
                return err
            }

            if _, err := db.Exec(`INSERT INTO example (name, created) 
            values ("Aaron", NOW())`); err != nil {
                return err
            }

            return nil
        }

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

        package database

        import (
            "database/sql"
            "fmt"

            _ "github.com/go-sql-driver/mysql" //we import supported 
            libraries for database/sql
        )

        // Query grabs a new connection
        // creates tables, and later drops them
        // and issues some queries
        func Query(db *sql.DB, name string) error {
            name := "Aaron"
            rows, err := db.Query("SELECT name, created FROM example 
            where name=?", name)
            if err != nil {
                return err
            }
            defer rows.Close()
            for rows.Next() {
                var e Example
                if err := rows.Scan(&e.Name, &e.Created); err != nil {
                    return err
                }
                fmt.Printf("Results:\n\tName: %s\n\tCreated: %v\n", 
                e.Name, e.Created)
            }
            return rows.Err()
        }

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

        package database

        // Exec replaces the Exec from the previous
        // recipe
        func Exec(db DB) error {

            // uncaught error on cleanup, but we always
            // want to cleanup
            defer db.Exec("DROP TABLE example")

            if err := Create(db); err != nil {
                return err
            }

            if err := Query(db, "Aaron"); err != nil {
                return err
            }
            return nil
        }

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

        package main

        import (
            "PacktPublishing/Go-Programming-Cookbook-Second-Edition/
             go-cookbook/chapter6/database"
            _ "github.com/go-sql-driver/mysql" //we import supported 
            libraries for database/sql
        )

        func main() {
            db, err := database.Setup()
            if err != nil {
                panic(err)
            }

            if err := database.Exec(db); err != nil {
                panic(err)
            }
        }

10. Run go run main.go.
11. You could also run the following command:

$ go build
$ ./example

You should see the following output:

$ go run main.go
Results:
 Name: Aaron
 Created: 2017-02-16 19:02:36 +0000 UTC

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