Fix link mixing

backend/mysql.go

@@ -116,11 +116,12 @@ func (s *Mysql) TryClickLink(slug string) *Link {
 
 func (s *Mysql) GetAllLinks() []*Link {
 	rows, err := s.db.Query("SELECT slug, url, clicks, created FROM links")
-	list := make([]*Link, 0)
+	list := make([]*Link, 0, 16)
 	if err != nil {
 		log.Println("mysql error: ", err)
 		return list
 	}
+	defer rows.Close()
 	for rows.Next() {
 		link := &internalLink{
 			Link: &Link{},

web.go

@@ -60,7 +60,11 @@ func (w *web) handleRoot(ctx *fasthttp.RequestCtx) {
 
 func (w *web) handleSlug(ctx *fasthttp.RequestCtx) {
 	log.Print(string(ctx.URI().Path()))
-	full := w.backend.TryClickLink(ctx.UserValue("slug").(string))
+
+	// Make a copy of a slug. fasthttp/router's UserValues become invalid after the request is completed.
+	slug := copyString(ctx.UserValue("slug").(string))
+
+	full := w.backend.TryClickLink(slug)
 
 	if full != nil {
 		ctx.Redirect(full.Url, fasthttp.StatusFound)
@@ -148,6 +152,13 @@ func (w *web) handleEdit(ctx *fasthttp.RequestCtx) {
 	ctx.SetStatusCode(fasthttp.StatusOK)
 }
 
+func copyString(in string) string {
+	var b strings.Builder
+	b.Grow(len(in))
+	b.WriteString(in)
+	return b.String()
+}
+
 type OperationError struct {
 	Error   bool   `json:"error"`
 	Message string `json:"message"`