Use config package to handle all controller configurations

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Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

cmd/root.go

@@ -98,6 +98,10 @@ func initConfig() {
 		viper.SetConfigType(configType)
 		viper.SetConfigName(configName)
 
+		// Viper will crash if you call 'WriteConfig()' and the file does
+		// not exists yet.
+		// Therefore we handle this case here.
+		// Inspired by //https://github.com/spf13/viper/issues/430#issuecomment-661945101
 		configPath := filepath.Join(configHome, configName+"."+configType)
 
 		_, err := os.Stat(configPath)