fix example

example/example.go

@@ -1,14 +0,0 @@
-package main
-
-import "github.com/alexflint/go-arg"
-
-func main() {
-	var args struct {
-		Input    string   `arg:"positional"`
-		Output   []string `arg:"positional"`
-		Verbose  bool     `arg:"-v,help:verbosity level"`
-		Dataset  string   `arg:"help:dataset to use"`
-		Optimize int      `arg:"-O,help:optimization level"`
-	}
-	arg.MustParse(&args)
-}

parse.go

@@ -1,17 +1,17 @@
 // Package arg parses command line arguments using the fields from a struct.
 // Any exported field is interpreted as a command line option, so
 //
-//    var args struct {
-//	    Iter int
-//      Debug bool
-//   }
-//   arg.MustParse(&args)
+//	var args struct {
+//		Iter int
+//		Debug bool
+//	}
+//	arg.MustParse(&args)
 //
 // defines two command line arguments, which can be set using any of
 //
-//    ./example --iter=1 --bar    // bar is a boolean flag so its value is optional
-//    ./example -iter 1           // bar will default to its zero value
-//    ./example --bar=true        // foo will default to its zero value
+//	./example --iter=1 --bar    // bar is a boolean flag so its value is optional
+//	./example -iter 1           // bar will default to its zero value
+//	./example --bar=true        // foo will default to its zero value
 //
 // The fastest way to learn how to use go-arg is to read the examples below.
 //
@@ -20,13 +20,13 @@
 //
 // Tags can be specified using the `arg` package name:
 //
-//    var args struct {
-//	    Input string   `arg:"positional"`
-//	    Log string     `arg:"positional,required"`
-//      Debug bool     `arg:"-d,help:turn on debug mode"`
-//      RealMode bool  `arg:"--real"
-//      Wr io.Writer   `arg:"-"`
-//   }
+//	var args struct {
+//		Input string   `arg:"positional"`
+//		Log string     `arg:"positional,required"`
+//		Debug bool     `arg:"-d,help:turn on debug mode"`
+//		RealMode bool  `arg:"--real"
+//		Wr io.Writer   `arg:"-"`
+//	}
 //
 // The valid tag strings are `positional`, `required`, and `help`. Further, any tag string
 // that starts with a single hyphen is the short form for an argument (e.g. `./example -d`),