kill running process in test golang

Writing a program based on http.ListenAndServe and writing the tests i've hit a stump. my test looks like this

package main

import (
    "testing"
    "../"
)

func TestServer(t *testing.T) {
    Server.Server()
}

and the tested function

package Server

import (
    "net/http"
)

var (
    DefaultPort = "8080"
    DefaultDir = "."
)

func Server() {
    port := DefaultPort
    directory := DefaultPort

    http.ListenAndServe(":"+port, http.FileServer(http.Dir(directory)))
}

my goal is to be able to run test and after the server listener is launched kill it and return a success message