remove support of go 1.21

[ktong]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.1%. Comparing base (bcdcfb9) to head (fe5e6e3).
Report is 28 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #122     +/-   ##
=======================================
- Coverage   69.2%   69.1%   -0.1%     
=======================================
  Files         24      24             
  Lines        760     756      -4     
=======================================
- Hits         526     523      -3     
+ Misses       193     192      -1     
  Partials      41      41             

Files	Coverage Δ
grpc/server.go	71.6% <ø> (-0.5%)	⬇️
http/server.go	67.9% <ø> (-0.4%)	⬇️
runner.go	100.0% <ø> (ø)

... and 1 file with indirect coverage changes