Introduction to Go Templates

Using templates in Go is a great way to produce content in a dynamic way. Go makes it possible to prepare content for display as pure text (by using the text/template package or as HTML with proper encoding (by using the html/template package). Both of these packages can be found in the Go standard library, and they are incredibly useful in presenting data neatly. In this blog post, I will introduce templates in Go by going over the steps to produce one line of formatted content from a template string.

The first step is to create a Go file called main.go that imports the necessary packages and defines the main function.

package main

import (
    "os"
    "text/template"
)

func main() {
    // insert code here
}

For this tutorial, I will be using a struct called Person, which can be defined as so:

type Person struct {
    Name       string
    Age        int
}

In main.go, we first initialize a new template called demo, and we then parse the template string to ensure there are no syntax errors. We use the panic function to handle errors quickly. We then execute the template using the Execute function which takes in two arguments: the first argument is to specify where you want the final report to be printed (this could be another file or the terminal). For this demo, the final report will be printed to the terminal (os.Stdout). The second argument specifies the data that is sent to the template string. In this demo, one instance of the struct Person is passed into the template string. Code for this step is shown below:

    person := Person{"Alex", 32}
    tmpl, err := template.New("demo").Parse("{{.Name}} is {{.Age}} years old")
    if err != nil {
        panic(err)
    }
    err = tmpl.Execute(os.Stdout, person)
    if err != nil {
        panic(err)
    }

In the template string, both the Name and Age attributes of the Person object are accessed by prepending a . to the attribute name. The . here represents the Person object. Main.go now looks like this:

package main

import (
    "os"
    "text/template"
)

type Person struct {
    Name       string
    Age        int
}

func main() {
    person := Person{"Alex", 32}
    tmpl, err := template.New("demo").Parse("{{.Name}} is {{.Age}} years old")
    if err != nil {
        panic(err)
    }
    err = tmpl.Execute(os.Stdout, person)
    if err != nil {
        panic(err)
    }
}

After running go run main.go, you will get the following output in the terminal:

Alex is 32 years old