func (c *Client) DoDeadline(req *Request, resp *Response, deadline time.Time) error {
	return clientDoDeadline(req, resp, deadline, c)
}
func (c *Client) DoDeadline(req *Request, resp *Response, deadline time.Time) error {
	return clientDoDeadline(req, resp, deadline, c)
}
// DoDeadline performs the given request and waits for response until
// the given deadline.
//
// Request must contain at least non-zero RequestURI with full url (including
// scheme and host) or non-zero Host header + RequestURI.
//
// Client determines the server to be requested in the following order:
//
//   - from RequestURI if it contains full url with scheme and host;
//   - from Host header otherwise.
//
// The function doesn't follow redirects. Use Get* for following redirects.
//
// Response is ignored if resp is nil.
//
// ErrTimeout is returned if the response wasn't returned until
// the given deadline.
//
// ErrNoFreeConns is returned if all Client.MaxConnsPerHost connections
// to the requested host are busy.
//
// It is recommended obtaining req and resp via AcquireRequest
// and AcquireResponse in performance-critical code.