Making prompted vars usable across the playbook - ansible

Question

I have one playbook with multiple tasks that have to run on different hosts.
In the beginning of the play I want to prompt the operator for their credentials which are the same for every host in the play. I want to have those credentials "stored" somewhere so they can be used across the tasks to log in on the provided host(s).
Playbook looks as followed,
---
- name: Ask for credentials
vars_prompt:
- name: username
prompt: "Username?"
- name: password
prompt: "Password?"
tasks:
- set_fact:
username: "{{username}}"
- set_fact:
password: "{{password}}"
- hosts: Host1
vars:
ansible_user: "{{ username }}"
ansible_password: "{{ password }}"
tasks:
- name: Do stuff
- hosts: Host2
vars:
ansible_user: "{{username}}"
ansible_password: "{{password}}"
tasks:
- name: Do stuff
...
From the moment the play hits the first task it will fail with the flowing error,
msg: 'The field ''remote_user'' has an invalid value, which includes an undefined variable. The error was: ''username'' is undefined'
Anyone that has experience in making prompted vars usable across the whole play and all tasks?

Answer 1

Q: "Make prompted vars usable across the whole play and all tasks>"
A: Run the first play with the group of all hosts that should be connected later. Run once the set_fact task. This will create the variables username and password for all hosts in the group.
For example if the group test_jails comprises hosts test_01, test_02, test_03 the play
- hosts: test_jails
vars_prompt:
- name: "username"
prompt: "Username?"
- name: "password"
prompt: "Password?"
tasks:
- set_fact:
username: "{{ username }}"
password: "{{ password }}"
run_once: true
- hosts: test_01
vars:
ansible_user: "{{ username }}"
ansible_password: "{{ password }}"
tasks:
- debug:
msg: "{{ ansible_user }} {{ ansible_password }}"
gives
ok: [test_01] => {
"msg": "admin 1234"
}