net: fix ExampleParseCIDR IPv4 prefix length

Issue #15228 describes that reserved address blocks should be used for
documentation purposes. This change updates the prefix length so the
IPv4 address adheres to this.

Change-Id: I237d9cce1a71f4fd95f927ec894ce53fa806047f
Reviewed-on: https://go-review.googlesource.com/42991
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/net/example_test.go b/src/net/example_test.go
index bfab21c5..979d817 100644
--- a/src/net/example_test.go
+++ b/src/net/example_test.go
@@ -44,7 +44,7 @@
 }
 
 func ExampleParseCIDR() {
-	ipv4Addr, ipv4Net, err := net.ParseCIDR("192.0.2.1/16")
+	ipv4Addr, ipv4Net, err := net.ParseCIDR("192.0.2.1/24")
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -60,7 +60,7 @@
 
 	// Output:
 	// 192.0.2.1
-	// 192.0.0.0/16
+	// 192.0.2.0/24
 	// 2001:db8:a0b:12f0::1
 	// 2001:db8::/32
 }