title: asp.net core docker issue
body: <p>I am new to docker and I developed a simple asp.net core webapi solution which uses a NuGet package from a private repository. </p>
  
  <p><em>dotnet restore</em> command returns an error for a missing NuGet package that is located inside a private repository which introduced in the nuget.config file inside the solution. </p>
  
  <p>does anyone knows what's the problem with my configs and dockerfile ?</p>
  
  <p>Dockerfile </p>
  
  <pre><code>FROM microsoft/aspnetcore-build:2.0 AS build-env
  WORKDIR /app
  
  # copy csproj and restore as distinct layers
  COPY *.csproj ./
  RUN dotnet restore
  
  # copy everything else and build
  COPY . ./
  RUN dotnet publish -c Release -o out
  
  # build runtime image
  FROM microsoft/aspnetcore:2.0
  WORKDIR /app
  COPY --from=build-env /app/out .
  ENTRYPOINT ["dotnet", "aspnetcoretssl.dll"]
  </code></pre>
  
  <p>.dockerignore</p>
  
  <pre><code>bin\
  obj\
  </code></pre>
  
  <p>Also I have a nuget.config file in the solution's root directory as below </p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;configuration&gt;
    &lt;packageSources&gt;
      &lt;add key="myrepo" value="\\path\to\the\nuget_packages_folder" /&gt;
      &lt;add key="nuget.org" value="https://api.nuget.org/v3/index.json" /&gt;
    &lt;/packageSources&gt;
  &lt;/configuration&gt; 
  </code></pre>
  
  <p>But I receive below messages from </p>
  
  <p><strong><em>docker build -t aspnetcoretssl .</em></strong></p>
  
  <blockquote>
    <p>error NU1101: Unable to find package TestContracts. No packages exist
    with this id in source(s): nuget.org   Generating MSBuild file
    /app/obj/aspnetcoretssl.csproj.nuget.g.props.</p>
    
    <p>The command '/bin/sh -c dotnet restore' returned a non-zero code: 1</p>
  </blockquote>