Success message in generic views doesn't work

Question

I am using Django generic views to create a success message, I searched a bit in stack overflow and seems like similar solution is not working in my case. views.py

class PostCreateView(CreateView):
    model = BlogPost
    template_name = 'blogs/blog-form.html'
    fields = [
        'title',
        'content',
        'image'
    ]
    success_message = 'Post added successfully!'

and here is the template wherein the messages should pop up.

<div class="wrapper">
    {% if messages %}
    {% for message in messages %}
    <div class="alert alert-success my-3">
        {{ message }}
    </div>
    {% endfor %}
    {% endif %}
    <a href="{% url 'blog:blog_update' object.slug %}" class="btn btn-success btn-sm">Update</a>
    <a href="{% url 'blog:blog_delete' object.slug %}" class="btn btn-danger btn-sm">Delete</a>
    <br><br>
    <img src="{{ object.image.url }}" class="image_in_list" alt="">
    <h2 class="display-4">{{ object.title }}</h2>
    <p>{{ object.content }}</p>
</div>

any help would be appreciated so much, thanks.