Spawn Objects Inside IEnumerator In Serverside (Unity Networking)

In my code, Bullets are spawn inside BulletSpawn Countie function looks like this

 IEnumerator BulletSpawn()
 {
         isFireCompleate = false;
         var bullteIns = Instantiate(Bullet, BulletSpawnPosition.transform.position, transform.localRotation);
         Destroy(bullteIns, 5f);
         yield return new WaitForSeconds(FireRate);
         isFireCompleate = true;
  }

And I am trying to add networking

I think for bullets: i want to spawn bullets inside the server side. and Using NetworkServer.Spawn(bullteIns), Sync bullet spawn to all the clients & Synchronize Damage (variable) using [SyncVar]

I'm following This presentation (Unite 2014 - New Unity Networking in 5.x).

 [Command]
 IEnumerator CmdBulletSpawn()

But with my countie function. i am not able to do that.

Error: Command function [PlayerInputController:CmdBulletSpawn] cannot be a coroutine

My Question is, How can i spawn bullets in the server side in this case. Is there any method beside using Command. or do i need to change my code.