How to create dictionary object from one fact from each host

Question

I am running ansible role to get package version on 50 servers. As example, I am looking to get output in form below

{
server1: "1.0",
server2: "1.0",
.
.
.
servert50: "1.1"
}

I have the logic to get the version but can't get a clear way to collect one fact from each run after role execution is finished.

The following didn't produce what I am looking for since it runs after each execution NOT once at the end. Also I need to have facts in list of dictionaries.

post_tasks:
- name: Print installed versions
  run_once: true
  copy:
    content: "{{ hostvars | to_nice_json }}"
    dest: /tmp/hostvar.json
  delegate_to: localhost