fix error in example code

[haifeiWu]

fix error in example code

[codecov-commenter]

Codecov Report

Base: 29.99% // Head: 31.14% // Increases project coverage by +1.14% 🎉

Coverage data is based on head (b2211d4) compared to base (a13f6f2).
Patch coverage: 69.56% of modified lines in pull request are covered.

❗ Current head b2211d4 differs from pull request most recent head 097a04f. Consider uploading reports for the commit 097a04f to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #546      +/-   ##
==========================================
+ Coverage   29.99%   31.14%   +1.14%     
==========================================
  Files          40       40              
  Lines        2967     2983      +16     
==========================================
+ Hits          890      929      +39     
+ Misses       2013     1988      -25     
- Partials       64       66       +2     

Impacted Files	Coverage Δ
...nts/naming_client/naming_http/naming_http_proxy.go	0.00% <0.00%> (ø)
common/nacos_server/nacos_server.go	16.98% <88.23%> (+15.37%)	⬆️
clients/naming_client/naming_http/beat_reactor.go	70.00% <100.00%> (-5.00%)	⬇️
.../naming_client/naming_cache/service_info_holder.go	27.36% <0.00%> (+2.10%)	⬆️

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