auth.go: use hashed/salted passwords instead of plaintext

data.go

@@ -43,14 +43,14 @@ func prepareDatabase() (*sql.DB, error) {
 	return db, nil
 }
 
-func getPasswordForUser(db *sql.DB, username string) (string, bool) {
-	var password string
+func getPasswordForUser(db *sql.DB, username string) ([]byte, bool) {
+	var password []byte
 
 	row := db.QueryRow("SELECT password FROM users WHERE username=$1", username)
 	err := row.Scan(&password)
 	if err != nil {
 		if err == sql.ErrNoRows {
-			return "", false
+			return nil, false
 		} else {
 			panic(err)
 		}