Environment variable mapping based on DeploymentStage parameter

template.yaml

Mappings:
  EnvironmentVariables:
    # mapping keys are the allowed values for DeploymentStage
    staging:
      # mapping value is multi-value where key is the environment variable
      PROD: false
      API_URL: {staging api endpoint url}
    production:
      PROD: true
      API_URL: {production api endpoint url}
      
Resources:
  HelloWorldFunction:
    # ...
    Environment:
      Variables:
        STAGE: !Ref DeploymentStage
        # instrinsic FindInMap function looks up the value by the deployment stage and the env var name
        PROD: !FindInMap [EnvironmentVariables, !Ref DeploymentStage, PROD]
        API_URL: !FindInMap [EnvironmentVariables, !Ref DeploymentStage, API_URL]