---
- hosts: mylist
  gather_facts: no
  pre_tasks:
    - name: get file name
      set_fact:
        fake_vault_file: "{{ inventory_hostname}}.txt"
    - name: get host specific creds from "fake" password vault
      set_fact:
        creds: "{{ lookup('file', fake_vault_file) |  from_yaml }}"
    - name: set username
      set_fact:
        ansible_user: "{{ creds.username }}"
    - name: set ssh_private_key_file
      set_fact:
        ansible_ssh_private_key_file:  "{{ creds.ssh_private_cred_file }}"
    - name:  run setup
      setup:

  tasks:
    - command: "ls"
      register: command_output