code: func FromHeader(r *http.Request) (*jwt.JSONWebToken, error) {
  	if r == nil {
  		return nil, ErrNilRequest
  	}
  	raw := ""
  	if h := r.Header.Get("Authorization"); len(h) > 7 && strings.EqualFold(h[0:7], "BEARER ") {
  		raw = h[7:]
  	}
  	if raw == "" {
  		return nil, ErrTokenNotFound
  	}
  	return jwt.ParseSigned(raw)
  }
docs: // FromHeader looks for the request in the
  // authentication header or call ParseMultipartForm
  // if not present.
  // TODO: Implement parsing form data.