сделал StringFromUpperCase()

micro/microfunctions.go

@@ -949,7 +949,12 @@ func StringFromUpperCase(s string) string {
 		return Otvet
 	}
 
-	Otvet = strings.ToUpper(Otvet[:1]) + Otvet[1:]
+	//преобразуем в руны т.к. есть русские буквы
+	MassRunes := []rune(Otvet)
+	MassRunes[0] = unicode.ToUpper(MassRunes[0])
+	Otvet = string(MassRunes)
+
+	//Otvet = strings.ToUpper(Otvet[:1]) + Otvet[1:]
 
 	return Otvet
 }

micro/microfunctions_test.go

@@ -464,6 +464,13 @@ func TestStringFromUpperCase(t *testing.T) {
 	if result := StringFromUpperCase("gOoD mOrNiNg"); result != "GOoD mOrNiNg" {
 		t.Errorf("Expected 'GOoD mOrNiNg', but got %s", result)
 	}
+
+	// Testing russian
+	result := StringFromUpperCase("продажа")
+	if result != "Продажа" {
+		t.Errorf("Expected 'Продажа', but got %s", result)
+	}
+
 }
 
 func TestStringFromLowerCase(t *testing.T) {