encoding/binary: make new example a bit more idiomatic

Mainly get rid of the weird zero-value struct literal,
but while we're here also group and order things a bit better:
first the reader, then the data, then the call (which takes reader then data).

Change-Id: I901b0661d85d8eaa0807e4482aac66500ca996c7
Reviewed-on: https://go-review.googlesource.com/78118
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

src/encoding/binary/example_test.go

@@ -52,18 +52,20 @@ func ExampleRead() {
 }
 
 func ExampleRead_multi() {
-	data := struct {
+	b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40, 0xff, 0x01, 0x02, 0x03, 0xbe, 0xef}
+	r := bytes.NewReader(b)
+
+	var data struct {
 		PI   float64
 		Uate uint8
 		Mine [3]byte
 		Too  uint16
-	}{}
-	b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40, 0xff, 0x01, 0x02, 0x03, 0xbe, 0xef}
-	buf := bytes.NewReader(b)
-	err := binary.Read(buf, binary.LittleEndian, &data)
-	if err != nil {
+	}
+
+	if err := binary.Read(r, binary.LittleEndian, &data); err != nil {
 		fmt.Println("binary.Read failed:", err)
 	}
+
 	fmt.Println(data.PI)
 	fmt.Println(data.Uate)
 	fmt.Printf("% x\n", data.Mine)