Nunjucks dynamic page template

i'm using nunjucks (gulp) as templating language and i want to build a dynamic page template.

This is my Json:

"pages": [
    {
        uname: "Welcome",
        title: "Page 1 Headline"
    },
    {
        uname: "About",
        title: "Page 2 Headline"
    }
]

Currently i have a static page (html) template for each page:

{% extends "layout.html" %}
{% set active_page = "Welcome" %} //<- This needs to be dynamicly
{% block content %}
<h1>{{ page[0].title }}</h1> //<- This needs to be dynamicly

My first thought was to read the url parameters but i couldn't solve it in this way.

Any suggestions?