How to make global variables on asp.net core 2 on level of all project web API ?

problem

How to make global variables on asp.net core 2 on level of all project web API ?

I work on asp.net core 2.1 project web API 

i have more controller and i need to use global variables for all solution or project shared CompanyCode value

so that how to do that on asp.net core 

so that how to make company code as global variables or session or shared if i call it in any controller i can get values ?