title: Nuget package restore error in Docker Compose build
body: <p>I am getting nugget restore error while building using docker-compose behind proxy. I have set proxy in docker for windows. Nuget restore works for command line <code>dotnet restore</code> and visual studio debug, but not using <code>docker-compose</code>.</p>
  
  <pre><code>:\Program Files\dotnet\sdk\2.1.104\NuGet.targets(104,5): error : Unable to load the service index for source https://api.nuget.org/v3/index.json. [C:\src\WebApp.sln]
  :\Program Files\dotnet\sdk\2.1.104\NuGet.targets(104,5): error :   An error occurred while sending the request. [C:\src\WebApp.sln]
  :\Program Files\dotnet\sdk\2.1.104\NuGet.targets(104,5): error :   A connection with the server could not be established [C:\src\WebApp.sln]
  ERROR: Service 'idenityapi' failed to build: The command 'powershell -Command $ErrorActionPreference = 'Stop'; $ProgressPreference = 'SilentlyContinue'; dotnet restore -nowarn:msb3202,nu1503' r
  turned a non-zero code: 1
  </code></pre>