refactor: Replace 'println' with 'fmt.Println'

[alexandear]

The PR replaces println with normal fmt.Println in the example/tokenauth.

println is not guaranteed to stay in the language according to the spec.

[gmlewis]

Thank you, @alexandear !
LGTM.
Merging.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.29%. Comparing base (2b8c7fa) to head (25eeb6f).
Report is 147 commits behind head on master.

Files with missing lines	Patch %	Lines
example/tokenauth/main.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3326      +/-   ##
==========================================
- Coverage   97.72%   93.29%   -4.43%     
==========================================
  Files         153      171      +18     
  Lines       13390    11729    -1661     
==========================================
- Hits        13085    10943    -2142     
- Misses        215      692     +477     
- Partials       90       94       +4     

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