Golang go routine concurrency behaviour not working as expected

Below is a simple go example. I have omitted error handling etc intentionally to make the example short. I have a simple for loop calling the writeOutput function 5 times using the go keyword to make the function run concurrently.

What I expect to happen is 5 files are created in /tmp/ with the contents of test.

What happens is that no files are created.

However if I remove the go keyword the code executes as expected. Im overlooking something super obvious. My background is dynamically typed languages like PHP/Ruby so just getting to grips with go and can't understand why 5 files are created when the go keyword exists.

package main
import (
  "os"
  "math/rand"
  "strconv"
)
func main() {
  for i := 0; i < 5; i++ {
   go writeOutput()
  }
}
func writeOutput() {
  filename := strconv.Itoa(rand.Intn(10000))
  file, _ := os.Create("/tmp/" + filename)
  defer file.Close()
  file.WriteString("test")
}

I managed to solve this with a wait group as suggested in the comments.

package main
import (
	"math/rand"
	"os"
	"strconv"
	"sync"
)
func main() {
	var wg sync.WaitGroup
	for i := 0; i < 5; i++ {
		wg.Add(1)
		go func() {
            defer wg.Done()
			writeOutput()
		}()
	}
	wg.Wait()
}
func writeOutput() {
	filename := strconv.Itoa(rand.Intn(10000))
	file, _ := os.Create("/tmp/" + filename)
	defer file.Close()
	file.WriteString("test")
}