“Unknown error executing Lambda packaging” Error During Packaging After Upgrading to .Net Core 2.0

Question

I changed the target framework from netcoreapp1.0 to netcoreapp2.0 in my .Net Core Lambda project.

When packaging the lambda I get an error executing the command dotnet lambda package -c Release -f netcoreapp2.0 :

Unknown error executing Lambda packaging: Could not find a part of the path

dotnet lambda package -c Release -f netcoreapp2.0
Executing publish command
Deleted previous publish folder
... invoking 'dotnet publish', working folder 'C:\Source\\Project.Lambda\bin\Release\netcoreapp2.0\publish'
... publish: Microsoft (R) Build Engine version 15.5.180.51428 for .NET Core
... publish: Copyright (C) Microsoft Corporation. All rights reserved.
... publish:   Restore completed in 32.96 ms for C:\Source\Project\Project.csproj.
... publish:   Restore completed in 50.69 ms for C:\Source\Project.Lambda\Project.Lambda.csproj.
... publish:   Restore completed in 80.61 ms for C:\Source\Project.Lambda\Project.Lambda.csproj.
... publish:   Project -> C:\Source\Project\bin\Release\netcoreapp2.0\Project.dll
... publish:   Project.Lambda -> C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\Project.Lambda.dll
... publish:   Project.Lambda -> C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\publish\
Flattening platform specific dependencies
... flatten: runtime/unix/lib/_._
Unknown error executing Lambda packaging: Could not find a part of the path 'C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\publish\runtime\unix\lib\_._'.
   at System.IO.Win32FileSystem.CopyFile(String sourceFullPath, String destFullPath, Boolean overwrite)
   at System.IO.File.InternalCopy(String sourceFileName, String destFileName, Boolean overwrite)
   at System.IO.File.Copy(String sourceFileName, String destFileName)
   at Amazon.Lambda.Tools.LambdaPackager.<>c__DisplayClass4_0.<FlattenRuntimeFolder>b__0(String sourceRelativePath)
   at Amazon.Lambda.Tools.LambdaPackager.FlattenRuntimeFolder(IToolLogger logger, String publishLocation, JsonData depsJsonTargetNode)
   at Amazon.Lambda.Tools.LambdaPackager.CreateApplicationBundle(LambdaToolsDefaults defaults, IToolLogger logger, String workingDirectory, String projectLocation, String configuration, String targetFramework, String& publishLocation, String& zipArchivePath)
   at Amazon.Lambda.Tools.Commands.PackageCommand.<ExecuteAsync>b__22_0()

Answer 1

It seems the issue occurred because I was using an old version of Amazon.Lambda.Tools :

<ItemGroup>
    <DotNetCliToolReference Include="Amazon.Lambda.Tools" Version="1.7.0" />
</ItemGroup>

Manually changing it to the latest version fixed it:

<ItemGroup>
    <DotNetCliToolReference Include="Amazon.Lambda.Tools" Version="2.1.2" />
</ItemGroup>

The output now looks like this:

Executing publish command
Deleted previous publish folder
... invoking 'dotnet publish', working folder 'C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\publish'
... publish: Microsoft (R) Build Engine version 15.5.180.51428 for .NET Core
... publish: Copyright (C) Microsoft Corporation. All rights reserved.
... publish:   Restoring packages for C:\Source\Project\Project.csproj...
... publish:   Restoring packages for C:\Source\Project.Lambda\Project.Lambda.csproj...
... publish:   Restore completed in 32.96 ms for C:\Source\Project\Project.csproj.
... publish:   Restore completed in 50.69 ms for C:\Source\Project.Lambda\Project.Lambda.csproj.
... publish:   Project -> C:\Source\Project\bin\Release\netcoreapp2.0\Project.dll
... publish:   Project.Lambda -> C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\linux-x64\Project.Lambda.dll
... publish:   Project.Lambda -> C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\publish\
Zipping publish folder C:\Source\Project.Lambda\bin\Release\netcoreapp2.0\publish to C:\Source\Project.Lambda\lambda.zip