Golang Viper config read into struct

config.go

package main

import (
	"fmt"

	"github.com/spf13/viper"
)

// Create private data struct to hold config options.
type config struct {
	Hostname string `yaml:"hostname"`
	Port     string `yaml:"port"`
}

// Create a new config instance.
var (
  conf *config
)
 
// Read the config file from the current directory and marshal
// into the conf config struct.
func getConf() *config {
	viper.AddConfigPath(".")
	viper.SetConfigName("config")
	err := viper.ReadInConfig()

	if err != nil {
		fmt.Printf("%v", err)
	}

	conf := &config{}
	err = viper.Unmarshal(conf)
	if err != nil {
		fmt.Printf("unable to decode into config struct, %v", err)
	}

	return conf
}

// Initialization routine.
func init() {
  // Retrieve config options.
  conf = getConf()
}

// Main program.
func main() {
  // Print the config options from the new conf struct instance.
  fmt.Printf("Hostname: %v\n", conf.Hostname) 
  fmt.Printf("Port: %v\n", conf.Port) 
}

config.yml

hostname: "localhost"
port: "9001"

what if i have nested config in yaml file. i did not work
thirdparty:
api:
key: "key1"
"baseUrl": "example.com"