Describe the bug
I am building a POC cloud function that has private dependencies and so have to rely on vendoring my dependencies. However, when trying to deploy the function, buildpack complains that it cannot find vendored dependencies for "github.com/GoogleCloudPlatform/functions-framework-go" despite it being used as an import and seeing the vendored files in the repo.

Full error message:

ERROR: (gcloud.functions.deploy) OperationError: code=3, message=Build failed with status: FAILURE and message: vendored dependencies must include "github.com/GoogleCloudPlatform/functions-framework-go"; if your function does not depend on the module, please add a blank import: _ "github.com/GoogleCloudPlatform/functions-framework-go/funcframework". For more details see the logs at https://console.cloud.google.com/cloud-build/builds;region=.

Additional context
How are you using GCP buildpacks?

• pack and the gcr.io/buildpacks/builder
• [:heavy_check_mark:] Cloud Functions
• Cloud Run
• Cloud Build
• App Engine Standard
• App Engine Flex

Did this used to work?
(Yes/No)
Not sure, this is my first time trying.

What language is your project primarily written in?
Go 1.21.0

Steps To Reproduce
Steps to reproduce the behavior:

1. gcloud command used:

gcloud functions deploy
${NAME}
--gen2
--no-allow-unauthenticated
--source .
--entry-point=${ENTRYPOINT}
--region=${REGION}
--trigger-http
--runtime=${RUNTIME}
--memory=${MEMORY}
--service-account=${SERVICE_ACCOUNT}
--env-vars-file=env-vars.yaml
${SECRETS_ARGS}

Expected behavior
Expected gcloud deploy command to be successful, or the error message to be correct or more descriptive.

Actual behavior
What actually happened?
Saw the following error message instead of a successful deploy:

ERROR: (gcloud.functions.deploy) OperationError: code=3, message=Build failed with status: FAILURE and message: vendored dependencies must include "github.com/GoogleCloudPlatform/functions-framework-go"; if your function does not depend on the module, please add a blank import: _ "github.com/GoogleCloudPlatform/functions-framework-go/funcframework". For more details see the logs at https://console.cloud.google.com/cloud-build/builds;region=.

If applicable, add screenshots / logs / error messages