fix net.Dial issue with ipv6

Author: BuckarooBanzay

cmd/client/ping.go

@@ -23,7 +23,7 @@ type PingResult struct {
 }
 
 func Ping(host string, port int) (*PingResult, error) {
-	conn, err := net.Dial("udp", fmt.Sprintf("%s:%d", host, port))
+	conn, err := net.Dial("udp", net.JoinHostPort(host, fmt.Sprintf("%d", port)))
 	if err != nil {
 		return nil, err
 	}

commandclient/client.go

@@ -32,7 +32,7 @@ func NewCommandClient(host string, port int) *CommandClient {
 }
 
 func (c *CommandClient) Connect() error {
-	conn, err := net.Dial("udp", fmt.Sprintf("%s:%d", c.Host, c.Port))
+	conn, err := net.Dial("udp", net.JoinHostPort(c.Host, fmt.Sprintf("%d", c.Port)))
 	if err != nil {
 		return err
 	}