title: golang prepend a string to a slice ...interface{}
body: <p>I've a method that has as an argument <code>v ...interface{}</code>, I need to prepend this slice with a <code>string</code>. Here is the method:</p>
  
  <pre><code>func (l Log) Error(v ...interface{}) {
    l.Out.Println(append([]string{" ERROR "}, v...))
  }
  </code></pre>
  
  <p>When I try with <code>append()</code> it doesn't work:</p>
  
  <pre><code>&gt; append("some string", v)
  first argument to append must be slice; have untyped string
  &gt; append([]string{"some string"}, v)
  cannot use v (type []interface {}) as type string in append
  </code></pre>
  
  <p>What's the proper way to prepend in this case?</p>