code: function vhostof (req, regexp) {
    var host = req.headers.host
    var hostname = hostnameof(req)
  
    if (!hostname) {
      return
    }
  
    var match = regexp.exec(hostname)
  
    if (!match) {
      return
    }
  
    var obj = Object.create(null)
  
    obj.host = host
    obj.hostname = hostname
    obj.length = match.length - 1
  
    for (var i = 1; i < match.length; i++) {
      obj[i - 1] = match[i]
    }
  
    return obj
  }
docs: Get the vhost data of the request for RegExp
  
  @param (object} req
  @param (RegExp} regexp
  @return {object}
  @private