You are given a code snippet that includes code for closing a database connection before the program terminates. Your task is to write a function that replicates the behavior of this code snippet by implementing the necessary steps to close a database connection.

Write a function `closeDBConnection()` that takes no parameters and closes the database connection. The function should have the following behavior:

1. Check if the global variable `global.Db` is initialized and not `nil`.
2. If `global.Db` is initialized and not `nil`, obtain the underlying database connection using the `.DB()` method.
3. Close the obtained database connection.
4. Print the message "Database connection closed successfully."

Note:
- The `global.Db` variable is of type `*sqlx.DB`, which represents the database connection.
- The `DB()` method returns a pointer to `*sql.DB`, the underlying database connection.
- The `global.Db.DB()` method returns two values - the first is the database connection, and the second is an error. In this case, we use a blank identifier to ignore the error.

Implement the `closeDBConnection()` function to meet the given requirements.
user
Sure, here's how you can implement the `closeDBConnection()` function in Go using your given requirements:

```go
import (
    "context"
    "errors"
    "log"
    "time"

    "database/sql"
    "database/sql/driver"
    "fmt"
    "os"

    "github.com/jmoiron/sqlx"
    _ "github.com/mattn/go-sqlite3" // Add this line to use SQLite driver
)

type DbConn struct {
    *sqlx.DB
}

// Function that closes the database connection in case of error
func closeDBConnection(err error) {
    if err != nil {
        close()
        log.Fatalf("An error occurred while closing the database. Error: %v\n", err)
    }
}

// Function to reopen a closed database connection
func DatabaseOpenInTx(ctx context.Context, conn *sqlx.DB) (*sqlx.Tx, error) {
    tx, err := conn.BeginTxC(ctx, nil)
    if err != nil {
        return nil, fmt.Errorf("Error opening transaction: %w", err)
    }
    return tx, nil
}

// Function to create a new SQLx connection to the database
func ConnectToDB(driver, path string) (*sqlx.DB, error) {
    // Connection options
    connOptions := sqlx.UseExecProvider(sqlx.NewEntries(*sqlx.NewStdOutDriver()))
    connOptions.Reset()

    // Establish connection
    db, err := sqlx.Connectx(context.Background(), fmt.Sprintf("%s::/%s", driver, path), connOptions)
    if err != nil {
        return nil, fmt.Errorf("Cannot connet to database. Error: %w", err)
    }

    return db, nil
}

func connectToBase() *sqlx.DB {
    base, err := sqlx.ConnectTo(context.Background(), "sqlite3", "base.db",
        sqlx.FromEnv(),
        sqlx.Options{
            Open: func() (*sqlx.DB, error) {
                db, err := sqlx.Connect(context.Background(), "sqlite3", "file:base.db?cache=shared&mode=rwc&_lock=exclusive&_tx isolation=default&parser=system&sslmode=disable",
                    [],
                    nil,
                )

                if err != nil {
                    return nil, err
                }

                return db, nil
            },
        },
    )

    handleError(err)

    return base
}

func init() {
    Db = connectToBase()

    // Custom driver to work with postgres in sqlx
    tx, err := DatabaseOpenInTx(context.Background(), Db)
    handleError(err)
    _, err = tx.Exec(`
        CREATE TABLE IF NOT EXISTS users (
            id SERIAL PRIMARY KEY,
            name TEXT NOT NULL,
            email TEXT NOT NULL,
            password TEXT NOT NULL
        );`)
    handleError(err)
}

// Close function that replicates the behavior of closing a connection
func close() {
    err := Db.Close()
    if err != nil {
        closeDBConnection(err)
    }

    log.Println("Database connection closed successfully.")
}
```

In this example, `Db` is a global variable initialized in `init()`, and `connectToBase()` connects to the database. The `close()` function closes the database connection, and if it fails, it prints an error message, as per your requirements.

Please remember that if `global.Db` is `nil`, the `.DB()` method returns a nil pointer. So, it's always better to check if the connection is established before trying to obtain the connection.
assistant
You are given a code snippet that includes code for closing a database connection before the program terminates. Your task is to write a function that replicates the behavior of this code snippet by implementing the necessary steps to close a database connection.

Write a function `closeDBConnection()` that takes no parameters and closes the database connection. The function should have the following behavior:

1. Check if the global variable `global.Db` is initialized and not `nil`.
2. If `global.Db` is initialized and not `nil`, obtain the underlying database connection using the `.DB()` method.
3. Close the obtained database connection.
4. Print the message "Database connection closed successfully."

Note:
- The `global.Db` variable is of type `*sqlx.DB`, which represents the database connection.
- The `DB()` method returns a pointer to `*sql.DB`, the underlying database connection.
- The `global.Db.DB()` method returns two values - the first is the database connection, and the second is an error. In this case, we use a blank identifier to ignore the error.

Implement the `closeDBConnection()` function to meet the given requirements.
user
Sure, I can help you write the `closeDBConnection()` function in Go based on your requirements. Here's how you might do it:

```go
import (
    "database/sql"
    _ "github.com/jmoiron/sqlx"
    "fmt"
)

var Db *sqlx.DB

func closeDBConnection() {
    // Check if the global variable Db is initialized and not nil
    if Db != nil {
        // Obtain the underlying database connection using the .DB() method
        dbConn, _ := Db.DB()

        // Close the obtained database connection
        err := dbConn.Close()
        if err != nil {
            fmt.Println("Error closing database connection:", err)
            return
        }

        // Print the message "Database connection closed successfully."
        fmt.Println("Database connection closed successfully.")
    } else {
        fmt.Println("Global variable Db is not initialized or nil.")
    }
}
```

This function first checks if the global variable `Db` is not `nil`. If it is not `nil`, it obtains the underlying database connection using the `.DB()` method. It then attempts to close the connection and prints a success message if it's successful. If there's an error while closing the connection, it prints the error message. If `Db` is `nil`, it prints a message indicating that the global variable is not initialized or `nil`.
assistant