chore: Remove deprecated build constraints

[alexandear]

This PR removes outdated // +build comments. The "Build constraints" says:

Go versions 1.16 and earlier used a different syntax for build constraints, with a "// +build" prefix. The gofmt command will add an equivalent //go:build constraint when encountering the older syntax.

NOTE: This change breaks compatibility with Go 1.16. The library will compile only with Go 1.17+.

[gmlewis]

Remember our discussion about "requiring" a minimum version of Go?
This is one of those things that allows this repo to require a minimum version of Go 1.16.
Once we make this change, Go 1.16 will no longer work with this repo.

Granted, it would seem weird to me that anyone might still want to use Go 1.16.

I'm totally fine to "move the bar" with this PR. However, we should probably leave this open for a week or so in order to allow anyone who cares deeply about this to respond.

Also, I'm thinking would should reinstate our attempt to keep track of the minimum Go version requirement in the README (and also attempt to keep it better up-to-date, which is my fault).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.29%. Comparing base (2b8c7fa) to head (a7e5792).
Report is 152 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3306      +/-   ##
==========================================
- Coverage   97.72%   93.29%   -4.43%     
==========================================
  Files         153      171      +18     
  Lines       13390    11729    -1661     
==========================================
- Hits        13085    10943    -2142     
- Misses        215      692     +477     
- Partials       90       94       +4     

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[gmlewis]

Thank you, @alexandear !
LGTM.

Allowing this PR to sit for one week until October 12, 2024 before merging in order to let other users of this repo to object to this change with their reasoning for retaining support for Go 1.16.

[gmlewis]

NOTE that if there are no objections to this PR breaking support for Go 1.16, we will proceed with the merge tomorrow.

[gmlewis]

@alexandear - would you mind adding to this PR a note in README.md that specifies that Go 1.17 is the minimum required version of the Go toolchain to use with this repo, please?

[alexandear]

@gmlewis added info about Go 1.17+, please check

[gmlewis]

@gmlewis added info about Go 1.17+, please check

Beautiful, thank you, @alexandear !
Merging.