move QUIC_GO_DISABLE_GSO check out of init

[jfgiorgi]

fix #4040

[marten-seemann]

isGSOSupported is only called once for every net.PacketConn that we handle, so there's really no point in caching the result.

Change LGTM.

[marten-seemann]

@jfgiorgi Would you prefer a patch release, or can this wait until the next regular release?

[codecov]

Codecov Report

Merging #4041 (3401e98) into master (824fd8a) will decrease coverage by 0.02%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #4041      +/-   ##
==========================================
- Coverage   83.28%   83.26%   -0.02%     
==========================================
  Files         147      147              
  Lines       14902    14898       -4     
==========================================
- Hits        12411    12404       -7     
- Misses       1990     1993       +3     
  Partials      501      501              

Files Changed	Coverage Δ
sys_conn_helper_linux.go	75.41% <50.00%> (+3.10%)	⬆️

... and 2 files with indirect coverage changes

[jfgiorgi]

@jfgiorgi Would you prefer a patch release, or can this wait until the next regular release?

We can wait.