title: Add unaltered lowercase headers to golang http request
body: <p>I am trying to set all-lowercase headers in a golang program and CanonicalMIMEHeaderKey is uppercasing the first letter. The API I am consuming only takes this particular header in all-lowercase at the moment. It's not an option to change that at this point in time. Is there a way to override that? </p>
  
  <p><a href="http://golang.org/pkg/net/textproto/#CanonicalMIMEHeaderKey" rel="nofollow">http://golang.org/pkg/net/textproto/#CanonicalMIMEHeaderKey</a></p>
  
  <p>So for example, the header I want to add is:</p>
  
  <pre><code>req.Header.Add("myheader", "myheadervalue")
  </code></pre>
  
  <p>But it comes out as:</p>
  
  <pre><code>req.Header.Add("Myheader", "myheadervalue")
  </code></pre>
  
  <p>Can anyone help please?</p>
  
  <p>Thanks</p>