go template是个模板替换的包，如果是普通text就使用text/template，如果是html还有html/template，其实有过jsp开发经验的人对这个东西应该很容易上手，它比那些jstl表达式要简单很多。下面看看基本使用

package main import ( "text/template" "os" ) type Friend struct { Fname string } type Person struct { UserName string Emails []string Friends []*Friend } func main() { f1 := Friend{Fname: "minux.ma"} f2 := Friend{Fname: "xushiwei"} t := template.New("fieldname example") //because f1 and f2 is struct(object) t,_ = t.Parse(`hello {{.UserName}}! {{range .Emails}} an email {{.}} {{end}} {{with .Friends}} {{range .}} my friend name is {{.Fname}} {{end}} {{end}} `) p := Person{UserName: "Astaxie",Emails: []string{"astaxie@beego.me","astaxie@gmail.com"},Friends: []*Friend{&f1,&f2}} t.Execute(os.Stdout,p) }

通过range遍历，with是用户获取对象的，输出结果
hello Astaxie!
an email astaxie@beego.me
an email astaxie@gmail.com
my friend name is minux.ma
my friend name is xushiwei

当然如果想对数据进行更复杂点的操作，可以通过独立的pipeline来处理数据。下面说一个复杂一点的用函数处理的例子：

package main

import (
    "fmt"
    "text/template"
    "os"
    "strings"
)

type Friend struct {
    Fname string
}

type Person struct {
    UserName string
    Emails   []string
    Friends  []*Friend
}

func EmailDealWith(args ...interface{}) string {
    ok := false
    var s string
    if len(args) == 1 {
        s,ok = args[0].(string)
    }
    if !ok {
        s = fmt.Sprint(args...)
    }
    // find the @ symbol
    substrs := strings.Split(s,"@")
    if len(substrs) != 2 {
        return s
    }
    // replace the @ by " at "
    return (substrs[0] + " at " + substrs[1])
}

func main() {
    f1 := Friend{Fname: "minux.ma"}
    f2 := Friend{Fname: "xushiwei"}
    t := template.New("fieldname example")
    t = t.Funcs(template.FuncMap{"emailDeal": EmailDealWith})
    t,_ = t.Parse(`hello {{.UserName}}! {{range .Emails}} an emails {{.|emailDeal}} {{end}} {{with .Friends}} {{range .}} my friend name is {{.Fname}} {{end}} {{end}} `)
    p := Person{UserName: "Astaxie",Emails:  []string{"astaxie@beego.me","astaxie@gmail.com"},&f2}}
    t.Execute(os.Stdout,p)
}

上面的 {{.|emailDeal}}是重点， {{.}}取的数据通过管道”|”交给函数处理，输出结果如下：
hello Astaxie!
an emails astaxie at beego.me
an emails astaxie at gmail.com
my friend name is minux.ma
my friend name is xushiwei

最后和大家一起看看ingress里面对模板的使用，先看看模板：

 {{range $name,$upstream := $backends}} upstream {{$upstream.Name}} { {{ if eq $upstream.SessionAffinity.AffinityType "cookie" }} sticky hash={{$upstream.SessionAffinity.CookieSessionAffinity.Hash}} name={{$upstream.SessionAffinity.CookieSessionAffinity.Name}} httponly; {{ else }} least_conn; {{ end }} {{ range $server := $upstream.Endpoints }}server {{ $server.Address }}:{{ $server.Port }} max_fails={{ $server.MaxFails }} fail_timeout={{ $server.FailTimeout }}; {{ end }} } {{ end }} {{ $limits := buildRateLimit $location }}

上面的代码是从Nginx.tmpl文件里面截取的两个点，一个是upstream构建用到range和下面limits构建用的函数buildRateLimit，遍历直接替换没有上面，看看函数定义吧：

funcMap = text_template.FuncMap{
        "empty": func(input interface{}) bool {
            check,ok := input.(string)
            if ok {
                return len(check) == 0
            }
            return true
        },"buildLocation":                buildLocation,"buildAuthLocation":            buildAuthLocation,"buildProxyPass":               buildProxyPass,"buildRateLimitZones":          buildRateLimitZones,"buildRateLimit":               buildRateLimit,"buildSSLPassthroughUpstreams": buildSSLPassthroughUpstreams,"buildResolvers":               buildResolvers,"isLocationAllowed":            isLocationAllowed,"buildLogFormatUpstream":       buildLogFormatUpstream,"contains":                     strings.Contains,"hasPrefix":                    strings.HasPrefix,"hasSuffix":                    strings.HasSuffix,"toUpper":                      strings.ToUpper,"toLower":                      strings.ToLower,}

定义了buildRateLimit，函数具体实现是

func buildRateLimit(input interface{}) []string {
    limits := []string{}

    loc,ok := input.(*ingress.Location)
    if !ok {
        return limits
    }

    if loc.RateLimit.Connections.Limit > 0 {
        limit := fmt.Sprintf("limit_conn %v %v;",loc.RateLimit.Connections.Name,loc.RateLimit.Connections.Limit)
        limits = append(limits,limit)
    }

    if loc.RateLimit.RPS.Limit > 0 {
        limit := fmt.Sprintf("limit_req zone=%v burst=%v nodelay;",loc.RateLimit.RPS.Name,loc.RateLimit.RPS.Burst)
        limits = append(limits,limit)
    }

    return limits
}

ok，介绍完毕