make go vet happy

examples/http-proxy/proxy.go

@@ -242,9 +242,7 @@ func addAddrToPeerstore(h host.Host, addr string) peer.ID {
 	return peerid
 }
 
-func main() {
-	flag.Usage = func() {
-		fmt.Println(`
+const help = `
 This example creates a simple HTTP Proxy using two libp2p peers. The first peer
 provides an HTTP server locally which tunnels the HTTP requests with libp2p
 to a remote peer. The remote peer performs the requests and 
@@ -256,7 +254,11 @@ Usage: Start remote peer first with:   ./proxy
 Then you can do something like: curl -x "localhost:9900" "http://ipfs.io".
 This proxies sends the request through the local peer, which proxies it to
 the remote peer, which makes it and sends the response back.
-`)
+`
+
+func main() {
+	flag.Usage = func() {
+		fmt.Println(help)
 		flag.PrintDefaults()
 	}