Example of creating a string that implements an interface in Go / golang: https://go.dev/play/p/-IC8BGzjPPG

string_interface.go

package main

import "fmt"

type A string

func (a A) Foo() {
	fmt.Printf("Foo: %q\n", a)
}

type Fooer interface {
	Foo()
}

func main() {
	var a Fooer
	a = A("hello")

	a.Foo()
}