code: func Prefix(p string) Option {
  	return Option(func(c *config) {
  		c.Client.Prefix += strings.TrimSuffix(p, ".") + "."
  	})
  }
docs: // Prefix appends the prefix that will be used in every bucket name.
  //
  // Note that when used in cloned, the prefix of the parent Client is not
  // replaced but is prepended to the given prefix.