ci: bump Go version to 1.18

[tdakkota]

No description provided.

[codecov]

Codecov Report

Merging #725 (2c63974) into main (7069fe2) will decrease coverage by 0.15%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #725      +/-   ##
==========================================
- Coverage   69.91%   69.76%   -0.16%     
==========================================
  Files         441      441              
  Lines       20970    20970              
==========================================
- Hits        14662    14630      -32     
- Misses       5383     5415      +32     
  Partials      925      925              

Impacted Files	Coverage Δ
telegram/updates/update.go	9.52% <0.00%> (-61.91%)	⬇️
telegram/internal/version/version.go	41.66% <0.00%> (-16.67%)	⬇️
telegram/updates/gap_buffer.go	71.42% <0.00%> (-10.72%)	⬇️
telegram/updates/state_channel.go	45.75% <0.00%> (-7.08%)	⬇️
telegram/updates/internal/e2e/server.go	65.38% <0.00%> (-6.16%)	⬇️
internal/mtproto/conn.go	92.22% <0.00%> (-3.34%)	⬇️
telegram/updates/state.go	48.71% <0.00%> (-2.57%)	⬇️
telegram/updates/sequence_box.go	80.53% <0.00%> (-0.89%)	⬇️
fileid/file_id.go	59.77% <0.00%> (+3.44%)	⬆️
fileid/photo_size_source.go	60.47% <0.00%> (+7.14%)	⬆️
... and 1 more

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