The client can be created using the RPC package's rpc.DialHTTP function, using the same host-port to obtain a client:

if len(os.Args) != 2 {
    log.Fatalln("Please specify an address.")
}
client, err := rpc.DialHTTP("tcp", os.Args[1])
if err != nil {
    log.Fatalln(err)
}
defer client.Close()

Then, we define a list of books that we are going to use for our example:

const hp = "H.P. Lovecraft"
var books = []common.Book{
    {ISBN: "1540335534", Author: hp, Title: "The Call of Cthulhu", Pages: 36},
    {ISBN: "1980722803", Author: hp, Title: "The Dunwich Horror ", Pages: 53},
    {ISBN: "197620299X", Author: hp, Title: "The Shadow Over Innsmouth", Pages: 40},
    {ISBN: "1540335534", Author: hp, Title: "The Case of Charles Dexter Ward", Pages: 176},
}

Considering that the format package prints the address of pointers to built-in types, we are going to define a helper function to show the pointer's content:

func callClient(client *rpc.Client, method string, in, out interface{}) {
    var r interface{}
    if err := client.Call(method, in, out); err != nil {
        out = err
    }
    switch v := out.(type) {
    case error:
        r = v
    case *int:
        r = *v
    case *bool:
        r = *v
    }
    log.Printf("%s: [%+v] -> %+v", method, in, r)
}

The client gets the operation to execute in the form of type.method, so we will be using the function like this:

callClient(client, "ReadingService.GetProgress", books[0].ISBN, new(int))
callClient(client, "ReadingService.AddBook", books[0], new(bool))
callClient(client, "ReadingService.AddBook", books[0], new(bool))
callClient(client, "ReadingService.GetProgress", books[0].ISBN, new(int))
callClient(client, "ReadingService.AddBook", books[1], new(bool))
callClient(client, "ReadingService.AddBook", books[2], new(bool))
callClient(client, "ReadingService.AddBook", books[3], new(bool))
callClient(client, "ReadingService.SetProgress", common.Progress{
    ISBN: books[3].ISBN,
    Pages: 10,
}, new(bool))
callClient(client, "ReadingService.GetProgress", books[3].ISBN, new(int))
callClient(client, "ReadingService.AdvanceProgress", common.Progress{
    ISBN: books[3].ISBN,
    Pages: 40,
}, new(bool))
callClient(client, "ReadingService.GetProgress", books[3].ISBN, new(int))

This will output each operation with its result.