Golang,MongoDB, Having issues using $in to find all elements with one string in there array property
<p>I am trying to find all users in a MongoDB collection that contains a  username string in the friends array. I am using Golang with the mgo driver. </p>

<pre><code>   type User struct {
    ...
        Friends        []string    `json: friends bson:"friends,omitempty"` 
    ...
    }

    ...
    // username is a string
    arr := []string{username}

    err := c.Find(bson.M{"friends": {"$in": arr}}).All(&amp;users)
    ...
</code></pre>

<p>I get this error:
http: panic serving [::1]:56358: assignment to entry in nil map</p>

<p>Any help would be greatly appreciated.</p>