go native

verb2

1. •
   To adopt the lifestyle or outlook of local inhabitants, especially when dwelling in a colonial region.

   • […]for St. Xavier's looks down on boys who ‘go native all-together.’ One must never forget that one is a Sahib, and that some day, when examinations are passed, one will command natives. — 1900
2. •
   Of a contractor or consultant, to begin working directly as an employee for a company and cease to work through a contracting firm or agency.