Task unmarshaling fails with aliases

[shahzzzam]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

Run this task:

version: v1.1.0
alias:
  values:
    repo: myrepo
steps:
  - build: -t $Registry/$repo:$ID  -t $Registry/hello-world:$ID -f Dockerfile .
  - push:
    - "$Registry/hello-world:$ID"

Expected behavior A clear and concise description of what you expected to happen.

Screenshots If applicable, add screenshots to help explain your problem.

Any relevant environment information

• OS: [e.g. Windows]
• Version [e.g. v1.0.0]

Additional context Add any other context about the problem here.