Trouble Referencing variable from a file in a custom var

[zacharyrote]

Using serverless 1.1.0

// env.yml
myUrl: http://localhost:8080/

// serverless.yml
env: ${file(…/env.yml)}
custom:
myUrl: ${self:env.myUrl}

// When accessing this value within a Plugin it appears that the value is not being interpreted correctly
let discoveryUrl = this.serverless.service.custom.discoveryUrl
console.log(discoveryUrl);

// Output
${self:env.myUrl}