AWS Serverless, CloudFormation : Error, Trying to populate non string value into a string for variable

I am using serverless framework for deploying my application on AWS Cloud.

https://serverless.com/

I want to use the value of AWS Account ID in my serverless.yml file and I want to export the acccount ID as the environment variable, so that it can be accessed from Lambda functions.

Based on the value of this lambda function, I want to create some resources ( like IAM roles, etc.), which refer to this accountId variable.

But when I try to deploy the stack, I get the below error,

Trying to populate non string value into a string for variable ${self:custom.accountId}. Please make sure the value of the property is a string.

My Serverless.yml file is as below

custom:
  accountId : !Ref "AWS::AccountId"


provider:
  name: aws
  runtime: go1.x
  stage: dev

  region: us-east-1

  environment:
     ACCOUNT_ID : ${self:custom.accountId}       
     myRoleArn: arn:aws:iam::${self:custom.accountId}:role/xxxxxxxx

Is there any way to refer to the value of the Account Id in the serverless.yml file?

You can't reference AWS::AccountId in your serverless.yml, because it doesn't quite translate when creating the CloudFormation template.

The workaround is to use the serverless plugin Pseudo Parameters.

You can install the plugin using npm.

npm install serverless-pseudo-parameters

You will also need to add the plugin to the serverless.yml file.

plugins:
  - serverless-pseudo-parameters

Then you can reference your AccountId with #{AWS::AccountId}

functions:
  helloWorld:
    handler: index.handler
    events:
      - http:
          path: /
          method: get
    environment:
      ACCOUNT_ID : #{AWS::AccountId}

Note that the reference begins with a hash instead of a dollar sign.