package main

import (
    "bytes"
    "fmt"
    "html/template"
    "log"
)

type Data struct {
    Name string
}

func main() {

    var tmpl *template.Template
    funcMap := template.FuncMap{
        "executeIfExists": func(name string, data interface{}) template.HTML {
            t := tmpl.Lookup(name)
            if t == nil {
                return ""
            } else {
                buf := bytes.NewBuffer([]byte{})
                err := t.Execute(buf, data)
                if err != nil {
                    log.Printf("Error executing template '%s': %v", name, err)
                    return ""
                } else {
                    return template.HTML(buf.Bytes())
                }
            }
        },
    }

    tmpl = template.Must(template.New("").Funcs(funcMap).ParseFiles("templates/main.tmpl", "templates/content.tmpl"))

    data := Data{
        Name: "John",
    }

    buf := bytes.NewBuffer([]byte{})
    err := tmpl.ExecuteTemplate(buf, "main.tmpl", data)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(string(buf.Bytes()))
}