output.txt

-> ansible-playbook -i test.ini test.yaml -kK  SSH password: 
sudo password [defaults to SSH password]: 

PLAY [all] ******************************************************************** 

GATHERING FACTS *************************************************************** 
ok: [localhost]

TASK: [shell whoami] ********************************************************** 
changed: [localhost]

TASK: [debug msg={{whoami.stdout}}] ******************************************* 
ok: [localhost] => {
    "msg": "root"
}

PLAY RECAP ******************************************************************** 
localhost                  : ok=3    changed=1    unreachable=0    failed=0

test.ini

[local]
localhost ansible_sudo_user=YOUR_USER_NAME

test.yaml

- hosts: all

  sudo: yes

  tasks:
    - shell: whoami
      register: whoami

    - debug: msg={{ whoami.stdout }}