Go templates and multiline string indentation

So I am trying to generate a YAML file by using the text/template package with a template value that is a multiline string. What I am struggling with is the indentation of the template string not being at the same level of the template variable in the tpl.

The (somewhat contrived example) here:

package main

import (
	"os"
	"text/template"
)

func main() {
	tpl := template.Must(template.New("yml").Parse(
		`routes:
  {{ . }}
`))

	value := `foo
bar`
	tpl.Execute(os.Stdout, value)
}

Playground: https://goplay.space/#2eK7_ELZTwA

The output I'd like to see here is obviously

routes:
  foo
  bar

and not

routes:
  foo
  bar

Is there some magic prefix to avoid this?

I was able to handle your requirements with the following code. I used the package sprig. It provides us with features that make it easy to achieve your goal. The code is as follows:

package main

import (
	"os"
	"text/template"

	"github.com/Masterminds/sprig/v3"
)

func main() {
	tpl := template.Must(template.New("yml").Funcs(sprig.FuncMap()).Parse(
		`routes:
{{ . | indent 2 }}
`))

	value := `foo
bar`
	tpl.Execute(os.Stdout, value)
}

I used the method Funcs to pass the functions into the template engine. These functions are returned from the invocation to sprig.FuncMap().
> Please note that you must invoke this function before the Parse otherwise it panics.

Then, I added the annotation | indent 2 to indent our lines by two characters. If you run the code, you'll get the desired output.

A complete list of the available function can be found here.
Let me know if this solves your issue, thanks!