Getting MissingMethodException when using standard libraries

I have a “factory” class tat sets up some dependency injection inside of my Aws Lambda:

var serviceProvider = new ServiceCollection()
                .AddHttpClient()
..... Other services

and when I run the test tool it throws back:

System.MissingMethodException: Method not found: 'Microsoft.Extensions.DependencyInjection.IServiceCollection Microsoft.Extensions.DependencyInjection.HttpClientFactoryServiceCollectionExtensions.AddHttpClient(Microsoft.Extensions.DependencyInjection.IServiceCollection)'.
   at Factories.ProcessorFactory.CreateProcessor()
   // Handle event method
   at Amazon.Lambda.TestTool.Runtime.LambdaExecutor.ProcessReturnAsync(ExecutionRequest request, Object lambdaReturnObject) in C:\codebuild\tmp\output\src142363207\src\Tools\LambdaTestTool\src\Amazon.Lambda.TestTool\Runtime\LambdaExecutor.cs:line 141
   at Amazon.Lambda.TestTool.Runtime.LambdaExecutor.ExecuteAsync(ExecutionRequest request) in C:\codebuild\tmp\output\src142363207\src\Tools\LambdaTestTool\src\Amazon.Lambda.TestTool\Runtime\LambdaExecutor.cs:line 62

Heres a dump of the aws-lambda-tools-defaults.json:

{
  "Information": [
    "This file provides default values for the deployment wizard inside Visual Studio and the AWS Lambda commands added to the .NET Core CLI.",
    "To learn more about the Lambda commands with the .NET Core CLI execute the following command at the command line in the project root directory.",
    "dotnet lambda help",
    "All the command line options for the Lambda command can be specified in this file."
  ],
  "profile": "default",
  "region": "eu-west-1",
  "configuration": "Release",
  "framework": "netcoreapp3.1",
  "function-runtime": "dotnetcore3.1",
  "function-memory-size": 256,
  "function-timeout": 30,
  "function-handler": "HandleStreamEvent"
}

[Diggzinc]

I would have to take the time to dig deeper into it.

But at first glance it might me that the tool has its own set of dependencies that somehow might be conflicting with the app. I would have to check how the assembly resolution is done when the application is attached to the tool to see if my guess is correct (since I believe the tool is what provisions the “runtime” while testing).

But then again this is just a wild guess, so take it with a grain of salt.

[stagha]

I am having this same problem with using libraries that have a Microsoft.AspNetCore dependency. I put together a test project. It builds but throws the MissingMethodException when run via the lambda test tool.

[Removed pending employer approval to upload source code]

Would appreciate some insight as we were forced to downgrade our lambda to .NET Core 2.1 in order to continue development. Thank you!