title: How to get the account id with cdk
body: <p>I wrote a simple typescript with AWS CDK and try to get the account id</p>
  
  <pre><code>import cdk = require("@aws-cdk/core");
  
  const app = new cdk.Stack();
  
  console.log(app.account);
  </code></pre>
  
  <p>But get below output</p>
  
  <pre><code>$ tsc index.ts 
  $ node index.js 
  ${Token[AWS::AccountId.0]}
  </code></pre>
  
  <p>So what's the meaning of <code>Token</code> here? How to get the real account id?</p>
  
  <h3>Updates</h3>
  
  <pre><code>$ cdk init app --language=typescript
  
  # replace lib/&lt;name&gt;-stack.ts with @Rob Raisch 's code
  
  $ cdk synth
  ${Token[AWS::AccountId.0]}
  Outputs:
    MyStackAccount:
      Description: Account of this stack
      Value:
        Ref: AWS::AccountId
  Resources:
    CDKMetadata:
      Type: AWS::CDK::Metadata
      Properties:
        Modules: aws-cdk=1.2.0,@aws-cdk/core=1.8.0,@aws-cdk/cx-api=1.8.0,jsii-runtime=node.js/v10.15.3
  
  $ cdk deploy
  ${Token[AWS::AccountId.0]}
  MyStack: deploying...
  MyStack: creating CloudFormation changeset...
   0/2 | 11:58:59 AM | CREATE_IN_PROGRESS   | AWS::CDK::Metadata | CDKMetadata Resource creation Initiated
   1/2 | 11:58:59 AM | CREATE_COMPLETE      | AWS::CDK::Metadata | CDKMetadata 
   2/2 | 11:59:00 AM | CREATE_COMPLETE      | AWS::CloudFormation::Stack | MyStack 
  
   ✅  MyStack
  
  Outputs:
  MyStack.MyStackAccount = 123456789012
  
  </code></pre>