format code with gofumpt

[thaJeztah]

• follow-up to context: various cleanups and improvements #3790
• relates to golangci-lint: enable more linters #3770
• relates to Use gofumpt if available, and enable gofumpt linter #3798

[codecov-commenter]

Codecov Report

Merging #3794 (6cc4f6f) into master (c39dfc3) will decrease coverage by 0.08%.
The diff coverage is 59.22%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3794      +/-   ##
==========================================
- Coverage   59.29%   59.21%   -0.09%     
==========================================
  Files         288      288              
  Lines       24640    24601      -39     
==========================================
- Hits        14610    14567      -43     
+ Misses       9160     9159       -1     
- Partials      870      875       +5