[ansible@ansible ~]$ cat > vault.pass <<'EOF'
12345
EOF

[ansible@ansible ~]$ chmod 0600 vault.pass 

[ansible@ansible ~]$ ansible-playbook 06-vault-test.yaml --vault-password-file vault.pass

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

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

TASK [debug] *******************************************************************
ok: [localhost] => {
    "msg": "DB password: SuperSecret123!"
}

PLAY RECAP *********************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0