TravisCI

It's recommended to first refer to the official instructions regarding using ShellCheck with Travis CI:
https://github.com/koalaman/shellcheck#travis-ci:

For a truly simple configuration, place the following in your .travis.yml:

language: shell
script:
  - bash -c 'shopt -s globstar; shellcheck **/*.{sh,ksh,bash}'

Note:

Travis CI has now integrated ShellCheck by default, so you don't need to manually install it.