import ( "fmt" "github.com/spf13/pflag" ) func main() { fs := pflag.NewFlagSet("myapp", pflag.ExitOnError) fs.String("foo", "", "foo description") // Mark the bar flag as deprecated and suggest using foo instead fs.MarkDeprecated("bar", "use --foo instead") fs.Parse([]string{"--bar", "value"}) fmt.Println(fs.Lookup("bar").Value.String()) }In this example, we create a new FlagSet and define a string flag called "foo". We then mark the "bar" flag as deprecated and suggest users use the "foo" flag instead. Finally, we parse the command-line arguments and print the value of the "bar" flag, which should be "value".