cookie.go
func (c *Cookie) Cookie() []byte {
	c.buf = c.AppendBytes(c.buf[:0])
	return c.buf
}
func (c *Cookie) Cookie() []byte {
	c.buf = c.AppendBytes(c.buf[:0])
	return c.buf
}
// Cookie returns cookie representation.
//
// The returned value is valid until the next call to Cookie methods.