refactor: enable gocritic linter and fix lint issues

[alexandear]

The PR enables gocritic in golangci-lint's config and fixes appeared lint issues:

❯ golangci-lint run
env.go:606:40: emptyStringTest: replace `len(fieldParams.OwnKey) > 0` with `fieldParams.OwnKey != ""` (gocritic)
        if fieldParams.Required && !exists && len(fieldParams.OwnKey) > 0 {
                                              ^
env.go:266:12: evalOrder: may want to evaluate Parse(&t) before the return statement (gocritic)
        return t, Parse(&t)
                  ^
env.go:273:12: evalOrder: may want to evaluate ParseWithOptions(&t, opts) before the return statement (gocritic)
        return t, ParseWithOptions(&t, opts)
                  ^
env.go:641:1: paramTypeCombine: func(key, defaultValue string, defExists bool, envs map[string]string) (val string, exists bool, isDefault bool) could be replaced with func(key, defaultValue string, defExists bool, envs map[string]string) (val string, exists, isDefault bool) (gocritic)
func getOr(key, defaultValue string, defExists bool, envs map[string]string) (val string, exists bool, isDefault bool) {
^
error.go:112:1: deprecatedComment: use `Deprecated: ` (note the casing) instead of `deprecated: ` (gocritic)
// deprecated: use VarIsNotSetError
^
error.go:130:1: deprecatedComment: use `Deprecated: ` (note the casing) instead of `deprecated: ` (gocritic)
// deprecated: use EmptyVarError
^
error.go:71:9: sprintfQuotedString: use %q instead of "%s" for quoted strings (gocritic)
        return fmt.Sprintf(`parse error on field "%s" of type "%s": %v`, e.Name, e.Type, e.Err)
               ^
error.go:92:9: sprintfQuotedString: use %q instead of "%s" for quoted strings (gocritic)
        return fmt.Sprintf(`no parser found for field "%s" of type "%s"`, e.Name, e.Type)
               ^
error.go:158:9: sprintfQuotedString: use %q instead of "%s" for quoted strings (gocritic)
        return fmt.Sprintf(`could not load content of file "%s" from variable %s: %v`, e.Filename, e.Key, e.Err)
               ^
env_test.go:279:25: stringConcatSimplify: suggestion: str1 + ":" + str2 (gocritic)
        t.Setenv("SEPSTRINGS", strings.Join([]string{str1, str2}, ":"))
                               ^
example_test.go:403:9: preferStringWriter: f.WriteString("super secret") should be preferred to the io.WriteString(f, "super secret") (gocritic)
        _, _ = io.WriteString(f, "super secret")
               ^

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (1f955b7) to head (d116bb4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #342   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          626       628    +2     
=========================================
+ Hits           626       628    +2     

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[ccoVeille]

I tend to copy paste the descriptions available for each linters.

You can find them in enabled-checks node of .golangci-lint.reference.yml

[ccoVeille]

I tend to enable them all or enable them by tags

and disable the noisy ones, explaining why.

This way new rules are added automatically. But I do that on the repositories I maintain

[caarlos0]

thanks!