playbook.yml

---
- hosts: localhost
  connection: local
  tasks:
    - debug:
        var: ansible_ssh_user
    - debug:
        message: "{{ item }}"
      with_items:
        - "{{ ansible_ssh_user }}"

run.txt

[lae@yuzu hack]$ ansible-playbook -i localhost, local_module_test.yml -K
SUDO password: 

PLAY [localhost] **********************************************************************************************************************************************************************************************************************************************

TASK [Gathering Facts] ****************************************************************************************************************************************************************************************************************************************
ok: [localhost]

TASK [debug] **************************************************************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "ansible_ssh_user": "lae"
}

TASK [debug] **************************************************************************************************************************************************************************************************************************************************
fatal: [localhost]: FAILED! => {"msg": "'ansible_ssh_user' is undefined"}
        to retry, use: --limit @/home/lae/hack/local_module_test.retry