connection not closed when database name is incorrect

[jatinn]

Describe the bug

If a database name is provided that does not exist, we get back an error however even though db.Close() is executed the network connection still remains open.

To Reproduce

package main

import (
	"context"
	"database/sql"
	"flag"
	"fmt"
	"os"
	"os/signal"

	_ "github.com/denisenkom/go-mssqldb"
)

func main() {
	var (
		username = "sa"
		password = "Password123"
		hostname = "127.0.0.1"
		port     = 1433
		database = flag.String("db", "master", "database name")
		count    = flag.Int("count", 1, "number of calls to make to the database")
	)

	flag.Parse()

	dsn := fmt.Sprintf("sqlserver://%s:%s@%s:%d?database=%s", username, password, hostname, port, *database)

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
	defer stop()

	for i := 0; i < *count; i++ {
		if err := doQuery(ctx, dsn); err != nil {
			fmt.Println("error running query", i+1, err.Error())
		} else {
			fmt.Printf("run %d done\n", i+1)
		}
	}
	fmt.Println("waiting for ctrl+c to exit")
	<-ctx.Done()
}

func doQuery(ctx context.Context, dsn string) error {
	db, err := sql.Open("sqlserver", dsn)
	if err != nil {
		return fmt.Errorf("error open db %w", err)
	}
	defer db.Close()

	row := db.QueryRowContext(ctx, "SELECT 1")
	var result int
	if err := row.Scan(&result); err != nil {
		return fmt.Errorf("error scanning row %w", err)
	}

	return nil
}

If you provide a database name that exists then should see the following, before sending the exit signal if you look for connections to the database it will be in TIME_WAIT

❯ go run main.go -db exists
run 1 done
waiting for ctrl+c to exit

# new terminal
❯ netstat -an | grep '1.1433'
tcp4       0      0  127.0.0.1.60859        127.0.0.1.1433         TIME_WAIT

However if you provide a database name that does not exist then the connection remains ESTABLISHED even though it should have been closed.

❯ go run main.go -db unknown
error running query 1 error scanning row mssql: login error: Cannot open database "unknown" that was requested by the login. Using the user default database "master" instead.
waiting for ctrl+c to exit

# new terminal
❯ netstat -an | grep '1.1433'
tcp4       0      0  127.0.0.1.1433         127.0.0.1.60894        ESTABLISHED
tcp4       0      0  127.0.0.1.60894        127.0.0.1.1433         ESTABLISHED

Expected behavior
The network connection should be closed

Further technical details

SQL Server version: docker image mcr.microsoft.com/mssql/server:2022-latest
Operating system: macOS 13.6.3