fix awaiting rollback function

[IvanKiral]

Motivation

Which issue does this fix? Fixes #51

If no issue exists, what is the fix or new feature? Were there any reasons to fix/implement things that are not obvious?

Checklist

• Code follows coding conventions held in this repo
• Automated tests have been added
• Tests are passing
• Docs have been updated (if applicable)
• Temporary settings (e.g. variables used during development and testing) have been reverted to defaults

How to test

1. Create a migration with a rollback function specified
2. Try to execute migration with --rollback switch

[codecov]

Codecov Report

Merging #52 (f72c71b) into master (3cd3ae7) will decrease coverage by 0.19%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #52      +/-   ##
==========================================
- Coverage   65.76%   65.58%   -0.19%     
==========================================
  Files           9        9              
  Lines         371      369       -2     
  Branches       98       96       -2     
==========================================
- Hits          244      242       -2     
  Misses        126      126              
  Partials        1        1              

Impacted Files	Coverage Δ
src/utils/migrationUtils.ts	58.19% <100.00%> (-0.68%)	⬇️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more