将YAML解组为struct

I am trying to parse a YAML data into a string:

package main

import (
    "fmt"
    "log"
    "gopkg.in/yaml.v2"
)

type Config struct {
    foo_bar string
}

func FailOnError(err error, msg string) {
    if err != nil {
        log.Fatalf("%s: %s", msg, err)
        panic(fmt.Sprintf("%s: %s", msg, err))
    }
}

func ParseYAMLConfig(data []byte) *Config {
    config := Config{}

    err := yaml.Unmarshal(data, &config)
    if err != nil {
        FailOnError(err, "Failed to unmarshal the config")
    }

    return &config
}

var configYAMLData = `
---
foo_bar: "https://foo.bar"
`

func main() {
    config := ParseYAMLConfig([]byte(configYAMLData))
    fmt.Printf("%v", config)
}

For some reason, config is an empty struct &{} though.