http.Error() func is used to send error messages and codes.

internal/handlers/handlers.go

@@ -38,14 +38,12 @@ func (h *CaptchaHandlers) Image(w http.ResponseWriter, r *http.Request) {
 
 	captchaImage, err := inmemdb.Image(captchaID, captchaStyle)
 	if err != nil {
-		w.WriteHeader(http.StatusNotFound)
-		fmt.Fprint(w, errMsgImageNotFound)
+		http.Error(w, errMsgImageNotFound, http.StatusNotFound)
 		return
 	}
 
 	if captchaImage == nil {
-		w.WriteHeader(http.StatusInternalServerError)
-		fmt.Fprint(w, errMsgFailedToGenImage)
+		http.Error(w, errMsgFailedToGenImage, http.StatusInternalServerError)
 		return
 	}
 
@@ -62,14 +60,12 @@ func (h *CaptchaHandlers) Solve(w http.ResponseWriter, r *http.Request) {
 
 	ok, err := inmemdb.Solve(captchaID, answer)
 	if err != nil {
-		w.WriteHeader(http.StatusNotFound)
-		fmt.Fprint(w, errMsgNotFound)
+		http.Error(w, errMsgNotFound, http.StatusNotFound)
 		return
 	}
 
 	if !ok {
-		w.WriteHeader(http.StatusForbidden)
-		fmt.Fprint(w, errMsgWrongAnswer)
+		http.Error(w, errMsgWrongAnswer, http.StatusForbidden)
 		return
 	}
 
@@ -80,22 +76,21 @@ func (h *CaptchaHandlers) IsSolved(w http.ResponseWriter, r *http.Request) {
 	captchaID := captcha.ID(server.GetURLParam(r, "captcha"))
 	isJustRemove := r.URL.Query().Has("remove")
 
-	w.WriteHeader(http.StatusNoContent)
-
 	if isJustRemove {
 		inmemdb.Remove(captchaID)
+		w.WriteHeader(http.StatusNoContent)
 		return
 	}
 
 	solved, err := inmemdb.IsSolved(captchaID)
 	if err != nil {
-		w.WriteHeader(http.StatusNotFound)
-		fmt.Fprint(w, errMsgNotFound)
+		http.Error(w, errMsgNotFound, http.StatusNotFound)
 		return
 	}
 
 	if !solved {
-		w.WriteHeader(http.StatusForbidden)
-		fmt.Fprint(w, errMsgWrongAnswer)
+		http.Error(w, errMsgWrongAnswer, http.StatusForbidden)
 	}
+
+	w.WriteHeader(http.StatusNoContent)
 }