func initConfig() {
	if cfgFile != "" {
		viper.SetConfigFile(cfgFile)
	} else {
		home, err := homedir.Dir()
		if err != nil {
			fmt.Println(err)
			os.Exit(1)
		}
		viper.AddConfigPath(home)
		viper.SetConfigName(".partialzip")
	}
	viper.AutomaticEnv()  
	if err := viper.ReadInConfig(); err == nil {
		fmt.Println("Using config file:", viper.ConfigFileUsed())
	}
}
initConfig reads in config file and ENV variables if set.
package cmd
import (
	"fmt"
	"os"
	homedir "github.com/mitchellh/go-homedir"
	"github.com/spf13/cobra"
	"github.com/spf13/viper"
)
var cfgFile string
var rootCmd = &cobra.Command{
	Use:   "punzip",
	Short: "Partially unzip remote zip archives",
}
func Execute() {
	if err := rootCmd.Execute(); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}
func init() {
	cobra.OnInitialize(initConfig)
}