Queue Imp in Go

Queue.go

package main

import "fmt"

type Collection []interface{}

type IQueue interface {
	insert(e interface{})
	pop() interface{}
	peek() interface{}
}

type IntQueue struct {
	queue Collection
}

func (queue *IntQueue) insert(e interface{}) {
	queue.queue = append(queue.queue, e)
}

func (queue *IntQueue) peek() (i interface{}, err error) {
	if len(queue.queue) > 0 {
		i := queue.queue[0]
		return i, nil
	}

	return nil, fmt.Errorf("Queue empty")
}

func (queue *IntQueue) pop() (i interface{}, err error) {
	ret, err := queue.peek()

	if err != nil {
		return nil, err
	}

	queue.queue = queue.queue[1:]

	return ret, nil
}

func printOutput(elem interface{}, err error) {
	if err == nil {
		fmt.Println(elem)
	} else {
		fmt.Println(err)
	}
}

func main() {
	queue := &IntQueue{}
	printOutput(queue.peek())
	printOutput(queue.pop())
	queue.insert(1)
	queue.insert(2)
	queue.insert(3)
	fmt.Println(queue.queue)
	printOutput(queue.peek())
	printOutput(queue.pop())
	fmt.Println(queue.queue)
}