options.go
func Prefix(p string) Option {
	return Option(func(c *config) {
		c.Client.Prefix += strings.TrimSuffix(p, ".") + "."
	})
}
func Prefix(p string) Option {
	return Option(func(c *config) {
		c.Client.Prefix += strings.TrimSuffix(p, ".") + "."
	})
}
// 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.