Is it necessary to put templates into a map for reusing in Go?

Question

To deal with every request in a web application, the normal code about templates is like this:

t:= template.New("welcome")
t, _ = t.ParseFiles("welcome.tpl")
t.Execute(w, data)

I guess ParseFiles every time cost a lot. Is it possible to reuse the template? So I improved it like this:

//templateMap := make(map[string][template])
//...
tplName :="welcome"
t := templateMap[tplName]
if t=nil{
    t:= template.New(tplName )
    t, _ = t.ParseFiles("welcome.tpl")
    templateMap[tplName] = t
}

t.Execute(w, data)

I wonder it is feasible or practicable to improve efficiency by putting templates into a map or a cache? I also wonder the function Execute is thread safe or not?

func (t *Template) Execute(wr io.Writer, data interface{}) (err error)

Answer 1

A template can actually act as a map of templates by itself. Here's what I do:

I declare a global template variable:

var t = template.New("master")

I don't actually use the "master" template, except as a container for other templates.

Then, I load all the templates when my app starts:

func init() {
    _, err := t.ParseGlob("templates/*.html")
    if err != nil {
        log.Fatalln("Error loading templates:", err)
    }
}

Then when I want to use one of the templates, I ask for it by name:

t.ExecuteTemplate(w, "user.html", data)