List of strings and ints in go?

I have no idea what I am doing and I decided to try out using a list (docs) in go. This is the most I can figure out

1. Why is %v printing {0xf840024660 <nil> 0xf840023660 4}?
2. Why am I not getting an error for mixing ints with strings?
3. How do I force a type? (such as ints only, strings only etc)

Code:

package main

import "fmt"
import "container/list"

func main() {
	ls := list.New()
	ls.PushBack("a")
	ls.PushBack(4)
	ls.PushBack("5")
	fmt.Println(ls)
	ls2 := list.New()
	ls2.PushBack(4)
	ls2.PushBack(8)
	fmt.Printf("%v\naaa\n", *ls2.Front())
	fmt.Println(*ls2.Back())
}

First off, you probably don't want container/list. You're probably looking for something like slices and append(). For example:

x := []int { 1, 2, 3 }
x = append(x, 4)
x = append(x, 5, 6)

The reason container/list lets you mix types is that it uses interface{} to hold values, and any type satisfies the empty interface.

To answer your first question for the calls to Front() and Back(), it is because you're printing out the Element struct which does not contain printable values. If you want to print the Element.Value you have to do (*ls2.Front()).Value. Similar reasons are true for why fmt.Println(ls) is printing weird.