add example.go

example/example.go

@@ -0,0 +1,14 @@
+package main
+
+import "github.com/alexflint/go-arg"
+
+func main() {
+	var args struct {
+		Input            string  `arg:"positional"`
+		Output           string  `arg:"positional"`
+		Foo              string  `arg:"help:this argument is foo"`
+		VeryLongArgument int     `arg:"help:this argument is very long"`
+		Bar              float64 `arg:"-b"`
+	}
+	arg.MustParse(&args)
+}