Switch Register() and Authenticate() to sql.Tx

Using sql.Tx (database transactions) instead of a plain database has the
advantage that the caller can wrap multiple library calls into one
transaction.

This guarantees that no database entries change between the library
calls which is critical to prevent race conditions.

1 files changed, 13 insertions, 17 deletions

diff --git a/password.go b/password.go
index edbeb7a..9be347a 100644
--- a/password.go
+++ b/password.go
@@ -12,34 +12,30 @@ const (
 	bcryptCost = 12
 )
 
-func Register(db *sql.DB, username, password string) error {
+func Register(tx *sql.Tx, username, password string) error {
 	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcryptCost)
 	if err != nil {
 		return err
 	}
 
-	err = Transaction(db, func(tx *sql.Tx) error {
-		_, err := tx.Exec(
-			`INSERT INTO users (username, password_bcrypt) VALUES(?, ?);`,
-			username,
-			hash,
-		)
-		return err
-	})
+	_, err = tx.Exec(
+		`INSERT INTO users (username, password_bcrypt) VALUES(?, ?);`,
+		username,
+		hash,
+	)
 
 	return err
 }
 
-func Authenticate(db *sql.DB, username, password string) error {
+func Authenticate(tx *sql.Tx, username, password string) error {
 	var hash []byte
-	err := Transaction(db, func(tx *sql.Tx) error {
-		row := tx.QueryRow(
-			`SELECT password_bcrypt from users WHERE username=?;`,
-			username,
-		)
 
-		return row.Scan(&hash)
-	})
+	row := tx.QueryRow(
+		`SELECT password_bcrypt from users WHERE username=?;`,
+		username,
+	)
+
+	err := row.Scan(&hash)
 	if err != nil {
 		return fmt.Errorf("Failed to get password hash from database: %w", err)
 	}