client.URL or client.BaseURL undefined behavior

[1Feng]

client.URL or client.BaseURL with empty host but port will send request to localhost

for example:

    // Create a new client
    cli := gentleman.New()

    // Define the Base URL
    // when host is empty, but port, there will cause an undefined behavior
    // cli.BaseURL(fmt.Sprintf("http://%s:%s", host, port))
    cli.BaseURL("http://:8889")  // or cli.URL("http://:8889")
    // fmt.Println(cli.Context.Request.URL.String())

    // Create a new request based on the current client
    req := cli.Request()

    // Method to be used
    req.Method("POST")

    // Define the JSON payload via body plugin
    data := map[string]string{"foo": "bar"}
    req.Use(body.JSON(data))

    // Perform the request, then it will send request to localhost
    res, err := req.Send()