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Powerful Command-Line Applications in Go

Using Viper for Configuration Management

Discover how to use Viper for flexible configuration management in Go command-line applications built with Cobra. Learn to bind configuration keys to flags, read from environment variables, and manage settings via config files to enhance your CLI tool's adaptability.

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When we use the Cobra generator to create the boilerplate code for our application, it automatically enables Viper. Viper is a configuration management solution for Go applications that allows us to specify configuration options for our application in several ways, including configuration files, environment variables, and command-line flags.

Defining the initConfig() function

Cobra enables Viper by running the function initConfig() when initializing the application. This function is defined in the cmd/root.go file:

Go (1.6.2)
func initConfig() {
  if cfgFile != "" {
    // Use config file from the flag.
    viper.SetConfigFile(cfgFile)
  } else {
    // Find home directory.
    home, err := homedir.Dir()
    if err != nil {
      fmt.Println(err)
      os.Exit(1)
    }
    // Search config in home directory with name ".pScan" (without extension).
    viper.AddConfigPath(home)
    viper.SetConfigName(".pScan")
  }
  viper.AutomaticEnv() // read in environment variables that match
  // If a config file is found, read it in.
  if err := viper.ReadInConfig(); err == nil {
    fmt.Println("Using config file:", viper.ConfigFileUsed())
  }
}
Defining the initConfig() function

If the user specifies a config file using the flag --config, Viper sets it as the configuration file for the application. If not, it sets the configuration file as the file $HOME/.pScan.yaml. Then it uses the function viper.AutomaticEnv() to read the configuration from environment ...