fix: Add .NET 8 runtime example

[Vlaaaaaaad]

Description

Added documentation for how this module can be used to deploy a tiny .NET 8 Lambda function.

Motivation and Context

TL;DR: Python annoyed me so much I decided to move to .NET 😅 Just like with Python, there are 30 different ways to package a .NET Lambda — this PR adds a super-simple dotnet8 example. To run this brew install --cask dotnet-sdk will probably be needed.

Late last year, after getting annoyed for the millionth time with Python's packaging (yes, I know uv and Flox exist), I decided to start moving some Lambdas to .NET. I was surprised to see no docs for how to use this module to deploy a dotnet8 Lambda — no examples, no issues, no discussions, no anything. Yesterday I finally remembered to create this Pull Request to update the docs 🙂

Just like with Python, there are a ton of ways to package a .NET Lambda:

• directly by running dotnet publish
• using the AWS Extensions for .NET CLI and running dotnet lambda package
• using AWS SAM and running sam package
• and so many other options

For all the above, of course, there are even more options:

• packaging can be done locally or in a container
• different runtimes can be used: dotnet8 (either .zip or container Lambdas), dotnet9 (container Lambdas only), or even custom runtimes
• the .NET code can be compiled using native ahead-of-time (AOT) compilation, which does make the package bigger but dramatically improves runtime performance, but that requires using an Amazon Linux 2023 image
• and so many other options and knobs and tweaks

In addition to me not having any idea how to do most of the above and in addition to me failing to do some of the above things (dotnet lambda package generates a zip already and getting that to play nicely with the package.py script from this module was... too much for me), adding all that would've been confusing and unnecessary. Plus, you know, a lot of code that would have had to be maintained and updated.

Finally I decided to add the most minimal example I could think of: a .NET8 Lambda using top-level statements (i.e. no classes and no factories and no 10 different .cs files) that's straightforward packaged in a .zip and ran using the AWS-maintained-and-managed dotnet8 runtime.
To actually run this, folks will need to install dotnet on their machines: either using the .NET installer or with Homebrew by running brew install --cask dotnet-sdk. The latest version of .NET should be installed (currently latest stable is 9 and latest long-term support is 8) as it can build packages for a lot of targets: from way before dotnet5 and all the way to dotnet9.

Breaking Changes

No breaking change for users of the module since this is a docs-only change.

For developers working on this module that want to run the examples/runtimes code, dotnet will have to be installed.

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects
• I have executed pre-commit run -a on my pull request

I also ran a terraform apply and confirmed the .NET 8 Lambda function was correctly created and that it was working. I commented out the other runtimes as I did not have the dependencies installed and I am ignoring the warning caused by the newly-released v6.0.0 of the AWS Terraform Provider:

Plan: 7 to add, 0 to change, 0 to destroy.

Changes to Outputs:
  + dotnet8_lambda_function_url  = (known after apply)
  + lambda_function_result       = {}
  + lambda_function_status_codes = {
      + dotnet8 = (known after apply)
    }
random_pet.this: Creating...
random_pet.this: Creation complete after 0s [id=pleasant-moccasin]
module.dotnet8_lambda_function.local_file.archive_plan[0]: Creating...
module.dotnet8_lambda_function.local_file.archive_plan[0]: Creation complete after 0s [id=6d4c946421e692953040ec9a9b61001dfbcfe686]
module.dotnet8_lambda_function.null_resource.archive[0]: Creating...
module.dotnet8_lambda_function.null_resource.archive[0]: Provisioning with 'local-exec'...
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): Executing: ["python3" "../../package.py" "build" "--timestamp" "1750341320306367000" "builds/92cf0e05b510d4bb6e4576ae3034c2b45cded791505c3dbd1aee936c2c857dd4.plan.json"]
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: creating 'builds/92cf0e05b510d4bb6e4576ae3034c2b45cded791505c3dbd1aee936c2c857dd4.zip' archive
module.dotnet8_lambda_function.aws_cloudwatch_log_group.lambda[0]: Creating...
module.dotnet8_lambda_function.aws_iam_role.lambda[0]: Creating...
module.dotnet8_lambda_function.aws_cloudwatch_log_group.lambda[0]: Creation complete after 1s [id=/aws/lambda/pleasant-moccasin-dotnet8]
module.dotnet8_lambda_function.aws_iam_role.lambda[0]: Creation complete after 2s [id=pleasant-moccasin-dotnet8]
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding content of directory: /Users/vlad/Developer/vlaaaaaaad/terraform-aws-lambda/examples/fixtures/runtimes/dotnet8/publish
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: Amazon.Lambda.Core.dll
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: Amazon.Lambda.RuntimeSupport.dll
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: Amazon.Lambda.Serialization.SystemTextJson.dll
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: SnapshotRestore.Registry.dll
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: bootstrap
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: bootstrap.deps.json
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: bootstrap.dll
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: bootstrap.pdb
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): zip: adding: bootstrap.runtimeconfig.json
module.dotnet8_lambda_function.null_resource.archive[0] (local-exec): Created: builds/92cf0e05b510d4bb6e4576ae3034c2b45cded791505c3dbd1aee936c2c857dd4.zip
module.dotnet8_lambda_function.null_resource.archive[0]: Creation complete after 5s [id=1582037579302064648]
module.dotnet8_lambda_function.aws_lambda_function.this[0]: Creating...
module.dotnet8_lambda_function.aws_lambda_function.this[0]: Still creating... [00m10s elapsed]
module.dotnet8_lambda_function.aws_lambda_function.this[0]: Creation complete after 11s [id=pleasant-moccasin-dotnet8]
module.dotnet8_lambda_function.aws_lambda_function_url.this[0]: Creating...
module.dotnet8_lambda_function.aws_lambda_function_url.this[0]: Creation complete after 0s [id=pleasant-moccasin-dotnet8]
data.http.this["dotnet8"]: Reading...
data.http.this["dotnet8"]: Read complete after 1s [id=https://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.lambda-url.eu-west-1.on.aws/]
╷
│ Warning: Deprecated attribute
│
│   on ../../outputs.tf line 9, in output "lambda_function_arn_static":
│    9:   value       = local.create && var.create_function && !var.create_layer ? "arn:${data.aws_partition.current.partition}:lambda:${data.aws_region.current.name}:${data.aws_caller_identity.current.account_id}:function:${var.function_name}" : ""
│
│ The attribute "name" is deprecated. Refer to the provider documentation for details.
│
│ (and 2 more similar warnings elsewhere)
╵

Apply complete! Resources: 7 added, 0 changed, 0 destroyed.

Outputs:

dotnet8_lambda_function_url = "https://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.lambda-url.eu-west-1.on.aws/"
lambda_function_result = {}
lambda_function_status_codes = {
  "dotnet8" = 200
}

Let me know if there's anything I missed or if I should change anything!

[antonbabenko]

Trying to run it on the Mac where dotnet has never existed before. brew install --cask dotnet executed successfully. What else should be installed? Maybe update the README.md or issue desciption.

│ RuntimeError: Script did not run successfully, exit code 1:  - The command could not be loaded, possibly because:
│   * You intended to execute a .NET application:
│       The application 'publish' does not exist.
│   * You intended to execute a .NET SDK command:
│       No .NET SDKs were found.
│ 
│ Download a .NET SDK:
│ https://aka.ms/dotnet/download
│ 
│ Learn about SDK resolution:
│ https://aka.ms/dotnet/sdk-not-found

[Vlaaaaaaad]

Oh god, this is embarrassing — I totally had the wrong instructions 🤦 The correct command to install .NET is brew install --cask dotnet-sdk, with the -sdk part. Installing dotnet adds only the runtime which, of course, can't compile code. I tested this on my machine and I can confirm that dotnet failed but dotnet-sdk worked.

@antonbabenko can you run a brew uninstall dotnet && brew install --cask dotnet-sdk please? I believe that should fix it. If it doesn't... I'l be very confused and go on a deeper dive into what is actually happening.

My apologies!

[antonbabenko]

It works!

[antonbabenko]

This PR is included in version 7.21.1 🎉

[antonbabenko]

Thank you for adding the example for the .NET runtime!

[Vlaaaaaaad]

Thank you for all your work on these awesome modules ❣️