了解gometalinter的警告：conn可以是io.Reader / io.Writer

After checking with gometalinter this part of code:

//ListenerButton is hanging listeners for contact button
func ListenerButton(number int, button *ui.Button, conn net.Conn) string {
    button.OnClicked(func(*ui.Button) {
        sliceMembers := []string{login, button.Text()}
        groupName = login + button.Text()
        _, err := conn.Write([]byte(JSONencode(login, "", "",
            0, groupName, 1,
            login, sliceMembers, " ", " ", "",
            " ", " ", " ", true, " ", "CreateGroup")))
        if err != nil {
            log.Println(err)
        }
        fmt.Println(login, groupName, number, "graphic 131")
    })
    return groupName
}

I've got this warning:

warning: conn can be io.Writer (interfacer)

What does it mean and how i have to resolve it?

That means that the ListenerButton function is only only using the Write method of conn. By changing the type from net.Conn to io.Writer, that allows your function to use a much larger number of io.Writer implementations. Having as small of interfaces as possible should be a goal when implementing your API.

With that change, for example, you could use an io.MultiWriter to write debug information to stderr, as well as the network connection:

func ListenerButton(number int, button *ui.Button, conn io.Writer) string {
    // ...
}

ListenerButton(number, button, io.MultiWriter(os.Stderr, networkConn))