refactor: use async API

[snitin315]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

No

Motivation / Use-Case

use async API

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #3719 (38541d1) into master (795f8cc) will decrease coverage by 0.28%.
The diff coverage is 84.61%.

❗ Current head 38541d1 differs from pull request most recent head c0af5e0. Consider uploading reports for the commit c0af5e0 to get more accurate results

@@            Coverage Diff             @@
##           master    #3719      +/-   ##
==========================================
- Coverage   92.87%   92.59%   -0.29%     
==========================================
  Files          14       14              
  Lines        1320     1323       +3     
  Branches      466      466              
==========================================
- Hits         1226     1225       -1     
- Misses         87       91       +4     
  Partials        7        7              

Impacted Files	Coverage Δ
lib/Server.js	93.46% <84.61%> (-0.38%)	⬇️

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[alexander-akait]

In future we should avoid sync API in favor async where it possible

[ylemkimon]

Please note graceful-fs doesn't patch fs.promises APIs: isaacs/node-graceful-fs#160.