reuse session_token across sessions so that you dont log urself out

lib/token.go

···
 	"encoding/hex"
 )
 
-func GenerateSessionToken() string {
-	// 32 bytes == 256 bits (AES security margin is 128 bits)
-	return generateSecureToken(32)
-}
-
-func generateSecureToken(length int) string {
+func GenerateSecureToken(length int) string {
 	b := make([]byte, length)
 	if _, err := rand.Read(b); err != nil {
 		return ""

site.go

···
 	if err != nil {
 		return fmt.Errorf("invalid password")
 	}
-	sessionToken := lib.GenerateSessionToken()
-	err = s.db.SetSessionToken(username, sessionToken)
+	sessionToken, err := s.db.GetSessionToken(username)
 	if err != nil {
-		log.Println(err)
+		return err
+	}
+	if sessionToken == "" {
+		sessionToken = lib.GenerateSecureToken(32)
+		err := s.db.SetSessionToken(username, sessionToken)
+		if err != nil {
+			return err
+		}
 	}
-
 	http.SetCookie(w, &http.Cookie{
 		Name:    "session_token",
 		Expires: time.Now().Add(time.Hour * 24 * 365),

sqlite/sql.go

···
 	return password
 }
 
+func (db *DB) GetSessionToken(username string) (string, error) {
+	var result sql.NullString
+	err := db.sql.QueryRow("SELECT session_token FROM user WHERE username=?", username).Scan(&result)
+	if err == sql.ErrNoRows {
+		return "", nil
+	}
+	return result.String, err
+}
+
 func (db *DB) SetSessionToken(username string, token string) error {
 	_, err := db.sql.Exec("UPDATE user SET session_token=? WHERE username=?", token, username)
 	return err