golang使用viper加载配置文件实现自动反序列化到结构

http_addr = ":8082"
grpc_addr = ":8083"
jaeger_url= "http://localhost:14268/api/traces"
tracing= true

type ConfigTest struct {
    HttpAddr  string `json:"http_addr" toml:"http_addr" yaml:"http_addr"`
    GrpcAddr  string `json:"grpc_addr" toml:"grpc_addr" yaml:"grpc_addr"`
    JaegerUrl string `json:"jaeger_url" toml:"jaeger_url" yaml:"jaeger_url" mapstructure:"jaeger_url"`
    Tracing   bool   `toml:"tracing"  json:"tracing" yaml:"tracing" ` // opentelemetry tracing
}

// jaeger 加载配置文件
func TestSourceFile_Unmarshal(t *testing.T) {
    filePath := "./test_toml.toml"
    viper.SetConfigFile(filePath)
    if err := viper.ReadInConfig(); err != nil {
        t.Error(err)
    }

    c := &ConfigTest{}
    if err := viper.Unmarshal(c); err != nil {
        t.Error(err)
    }
    logger.Infow("Unmarshal file sucess", "v", c)
}

func (v *Viper) Unmarshal(rawVal interface{}, opts ...DecoderConfigOption) error {
    return decode(v.AllSettings(), defaultDecoderConfig(rawVal, opts...))
}
func decode(input interface{}, config *mapstructure.DecoderConfig) error {
    decoder, err := mapstructure.NewDecoder(config)
    if err != nil {
        return err
    }
    return decoder.Decode(input)
}
func NewDecoder(config *DecoderConfig) (*Decoder, error) {
    if config.TagName == "" {
        config.TagName = "mapstructure"
    }
    // ...
}

func TestSourceFile_Unmarshal1(t *testing.T) {
    filePath := "./test_toml.toml"
    c := &ConfigTest{}
    if err := viperUnmarshal(c, filePath); err != nil {
        t.Error(err)
    }
    logger.Infow("Unmarshal file sucess", "v", c)
}
func viperUnmarshal(v interface{}, configPath string) error {
    var tagName string
    ext := filepath.Ext(configPath)
    if len(ext) > 1 {
        tagName = ext[1:]
    }
    // set decode tag_name, default is mapstructure
    decoderConfigOption := func(c *mapstructure.DecoderConfig) {
        c.TagName = tagName
    }
    cViper := viper.New()
    cViper.SetConfigFile(configPath)
    if err := cViper.ReadInConfig(); err != nil {
        return err
    }
    return cViper.Unmarshal(v, decoderConfigOption)
}