plugin: fix doc example fmt usage
plugin: fix doc example fmt usage

Change-Id: I0520a37a48a56d231a8ac2dc58b2bf1762282760
Reviewed-on: https://go-review.googlesource.com/32795
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

polyverse-security/go,ImJasonH/go,linux-on-ibm-z/go,golang/go,linux-on-ibm-z/go,derekmarcotte/go,cloudflare/go,cloudflare/go,goodlang/good,golang/go,Cofyc/go,akutz/go,codestation/go,suncycheng/go,Cofyc/go,ImJasonH/go,cloudflare/go,vsekhar/elastic-go,codestation/go,suncycheng/go,codestation/go,CAFxX/go,ImJasonH/go,Cofyc/go,linux-on-ibm-z/go,golang/go,derekmarcotte/go,codestation/go,codestation/go,codestation/go,golang/go,polyverse-security/go,nawawi/go,josharian/go,CAFxX/go,cloudflare/go,polyverse-security/go,CAFxX/go,vsekhar/elastic-go,CAFxX/go,vsekhar/elastic-go,vsekhar/elastic-go,polyverse-security/go,akutz/go,Cofyc/go,suncycheng/go,josharian/go,polyverse-security/go,nawawi/go,cloudflare/go,nawawi/go,Cofyc/go,golang/go,ImJasonH/go,akutz/go,vsekhar/elastic-go,derekmarcotte/go,polyverse-security/go,golang/go,suncycheng/go,derekmarcotte/go,derekmarcotte/go,linux-on-ibm-z/go,golang/go,cloudflare/go,akutz/go,vsekhar/elastic-go,derekmarcotte/go,vsekhar/elastic-go,CAFxX/go,codestation/go,Cofyc/go,linux-on-ibm-z/go,akutz/go,CAFxX/go,suncycheng/go,nawawi/go,cloudflare/go,Cofyc/go,ImJasonH/go,linux-on-ibm-z/go,derekmarcotte/go,CAFxX/go,goodlang/good,josharian/go,derekmarcotte/go,ImJasonH/go,polyverse-security/go,goodlang/good,josharian/go,goodlang/good,christopher-henderson/Go,suncycheng/go,nawawi/go,codestation/go,linux-on-ibm-z/go,nawawi/go,suncycheng/go,ImJasonH/go,Cofyc/go,golang/go,goodlang/good,goodlang/good,josharian/go,akutz/go,cloudflare/go,josharian/go,linux-on-ibm-z/go,nawawi/go,josharian/go,akutz/go,josharian/go,polyverse-security/go,akutz/go,goodlang/good,CAFxX/go,suncycheng/go,goodlang/good,ImJasonH/go,nawawi/go,vsekhar/elastic-go