import ( "fmt" "go4.org/jsonconfig" ) func main() { // Parse a JSON configuration file conf, err := jsonconfig.ParseFile("config.json") if err != nil { panic(err) } // Get the value of a "foo" configuration option foo := conf.Obj("options").OptionalString("foo", "default") // Print the value of foo fmt.Println(foo) }In this example, we parse a configuration file and then use the OptionalString method to get the value of a "foo" configuration option. If the option is not present in the configuration file, the method returns the default value "default". This can be useful for handling optional configuration options that may not be present in every configuration file. The package library is go4.org.jsonconfig.