title: Environment variables not visible in configuration provider
body: <p>I'm trying to set up database connection string for my Azure Devops Entity Framework database migration task.</p>
  
  <p>My idea is not to publish config with database connections on git but to use environment variables to override app config with production settings (DB connection string).</p>
  
  <p>When migration is started, set environment variable is not read by app, instead, default, dev connection string is used.</p>
  
  <p>For example connection string entry is: <code>ConnectionStrings.Database</code></p>
  
  <p>I have set it like this: <code>set ASPNETCORE_ConnectionStrings__Database=test</code></p>
  
  <p>I does not work.
  When I set connection string in Visual Studio Debug properties it works properly.
  I have included environment variables in app startup, as MS documentation suggests.</p>
  
  <p>What is the difference between VS debugger set variables and console set ones?</p>
  
  <p>Thank you for your help. </p>
  
  <p>UPDATE:
  Visual Studio add's environment variables to <code>launchSettings.json</code>
  <img src="https://i.stack.imgur.com/eaZSv.png" /></p>