Chore(fix): set asynctimerchan=1 on build

[walldiss]

Set go:debug directive "asynctimerchan=1" until golang/go#69312 is fixed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.50%. Comparing base (2469e7a) to head (e092fac).
Report is 196 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3761      +/-   ##
==========================================
+ Coverage   44.83%   45.50%   +0.67%     
==========================================
  Files         265      281      +16     
  Lines       14620    16059    +1439     
==========================================
+ Hits         6555     7308     +753     
- Misses       7313     7905     +592     
- Partials      752      846      +94     

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[Wondertan]

Let's do it in go.mod instead as per (https://go.dev/doc/godebug). The main file also works, but it's buried somewhere deep instead of top level go.mod