A .NET Core Lambda deployment package is a zip file of your function's compiled assembly along with all of its assembly dependencies. The package also contains a proj.deps.json file. This signals to the .NET Core runtime all of your function's dependencies and a proj.runtimeconfig.json file, which is used to configure the .NET Core runtime. The .NET CLI’s publish command can create a folder with all of these files, but by default the proj.runtimeconfig.json will not be included because a Lambda project is typically configured to be a class library. To force the proj.runtimeconfig.json to be written as part of the publish process, pass in the command line argument: /p:GenerateRuntimeConfigurationFiles=true to the publish command.
Note
Although it is possible to create the deployment package with the dotnet publish command, we suggest you create the deployment package with either the AWS Toolkit for Visual Studio or the .NET Core CLI. These are tools optimized specifically for Lambda to ensure the lambda-project.runtimeconfig.json file exists and optimizes the package bundle, including the removal of any non-Linux-based dependencies.