Only perform root check on non-windows systems.

Is anyone using go-sendxmpp on windows?

main.go

@@ -172,17 +172,20 @@ func main() {
 		log.Fatal("Can't use message type headline for groupchat messages.")
 	}
 
-	// Get the current user.
-	currUser, err := osUser.Current()
-	if err != nil {
-		log.Fatal("Failed to get current user: ", err)
-	}
-	if currUser.Username == "root" {
-		fmt.Println("WARNING: It seems you are running go-sendxmpp as root user.\n" +
-			"This is is not recommended as go-sendxmpp does not require root " +
-			"privileges. Please consider using a less privileged user. For an " +
-			"example how to do this with sudo please consult the manpage chapter " +
-			"TIPS.")
+	// Print a warning if go-sendxmpp is run by the user root on non-windows systems.
+	if runtime.GOOS != "windows" {
+		// Get the current user.
+		currUser, err := osUser.Current()
+		if err != nil {
+			log.Fatal("Failed to get current user: ", err)
+		}
+		if currUser.Username == "root" {
+			fmt.Println("WARNING: It seems you are running go-sendxmpp as root user.\n" +
+				"This is is not recommended as go-sendxmpp does not require root " +
+				"privileges. Please consider using a less privileged user. For an " +
+				"example how to do this with sudo please consult the manpage chapter " +
+				"TIPS.")
+		}
 	}
 
 	switch *flagSCRAMPinning {