package main import ( "fmt" "os" "github.com/codegangsta/cli" ) func main() { app := cli.NewApp() app.Name = "myprogram" app.Usage = "do some things" app.Action = func(c *cli.Context) { if c.NArg() > 0 { fmt.Println("Hello", c.Args()[0]) } else { fmt.Println("Hello, world!") } } app.Run(os.Args) }In this example, we create a new CLI application using the NewApp() function from the codegangsta/cli library. We then set the name and usage of the app, and define the app's main action using the Action property. The action function takes a Context argument, which provides access to the parsed command line arguments. In the action function, we check if the user has provided any arguments using the NArg() function, and if so, print a personalized greeting. Otherwise, we print a generic greeting. This is just a simple example, but the Context Args functionality can be used to parse any number and type of command line arguments, making it a powerful tool for building robust CLIs in Go.