简单的XML解组返回空值

I'm trying a unmarshal some basic XML in Go. I've been able to unmarshal very large XML files in Go before, so the issue I have here really baffles me.

Unmarshalling finds one item, as it should, but all values are to their null default: strings are empty and the float is zero.

Any hint would help. Thanks.

XML

<config><throttle delay="20" unit="s" host="feeds.feedburner.com"/></config>

Output

host:"", unit:"", delay:0.000000

Code

package main

import (
    "encoding/xml"
    "fmt"
)

// Config allows for unmarshling of the remote configuration file.
type Config struct {
    XMLName    xml.Name     `xml:"config"`
    Throttlers []*Throttler `xml:"throttle"`
}

// Throttler stores the throttle information read from the configuration file.
type Throttler struct {
    host  string  `xml:"host,attr"`
    unit  string  `xml:"unit,attr"`
    delay float64 `xml:"delay,attr"`
}

func main() {

    data := `
        <config><throttle delay="20" unit="s" host="feeds.feedburner.com"/></config>
    `
    config := Config{}
    err := xml.Unmarshal([]byte(data), &config)
    if err != nil {
        fmt.Printf("error: %config", err)
        return
    }
    thr := config.Throttlers[0]
    fmt.Println(fmt.Sprintf("host:%q, unit:%q, delay:%f", thr.host, thr.unit, thr.delay))

}

Go playground link here

Just as trivially, the Throttler struct doesn't export its fields. Hence, changing the struct to have upper case variables makes them accessible.

Fixed example here