chore: attempt to fix some gomod issue

[thinkerou]

#1604 #1566 #1700 #1737

because some dependencies only are used on example i.e. grpc.

Or migrate examples to gin-gonic/examples`?

[codecov]

Codecov Report

Merging #1751 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1751   +/-   ##
=======================================
  Coverage   98.48%   98.48%           
=======================================
  Files          41       41           
  Lines        2042     2042           
=======================================
  Hits         2011     2011           
  Misses         19       19           
  Partials       12       12

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