layers sam template

layer.js

  myFunction: 
    Type: AWS::Serverless::Function
    Properties:
      Handler: test.handler
      Runtime: nodejs12.x
      Timeout: 3
      Layers:
        - Ref: MyLayer

  MyLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      LayerName: MyLayer
      Description: Layer description
      ContentUri: 'mylayer/'
      CompatibleRuntimes:
        - nodejs12.x
      LicenseInfo: 'Available under the MIT-0 license.'
      RetentionPolicy: Retain