Viper is not considering the yaml tags in my structs on unmarshalling

Question

when I use the Unmarshal method of viper to fill my config structs with the values in my yaml file, some of the struct fields became empty! I do it in this way:

viper.SetConfigType("yaml")
viper.SetConfigName("config")
viper.AddConfigPath("/etc/myapp/")
viper.AddConfigPath(".")

err := viper.ReadInConfig()
// error checking ...
conf := &ConfYaml{}
err = viper.Unmarshal(conf)
// error checking ...

And my structs are like this:

type ConfYaml struct {
    Endpoints SectionStorageEndpoint `yaml:"endpoints"`
}

type SectionStorageEndpoint struct {
    URL       string `yaml:"url"`
    AccessKey string `yaml:"access_key"`
    SecretKey string `yaml:"secret_key"`
    UseSSL    bool   `yaml:"use_ssl"`
    Location  string `yaml:"location"`
}

Here the url and location fields are filled with proper value in the yaml file, but the other fields are empty!

It's wondering that when I try to print a field like:

viper.Get("endpoints.access_key")

it prints the proper value in the yaml file and is not empty!!

Answer 1

Finally found the solution, changing yaml: tags to mapstructure: will fix the problem.

It seems that viper couldn't unmarshal the fields that haven't the same key name in my .yaml file. Like the access_key and secret_key in the question, cause the struct fields where AccessKey and SecretKey.

But the fields like location and url that had the same name in the struct and .yaml file, and there was no problem.

As this issue says:

The problem is that viper uses mapstructure package for unmarshalling config maps to structs. It doesn't support yaml tags used by the yaml package.

So changing the yaml: in the tags to mapstructure: had fixed the problem.