How To Make A Calculate Basic Math, Program Console With VB.Net

i make a simple program to calculate basic math....

 Sub main()
        Dim a, b, luas, jari, keliling As Integer
        Dim menu, sisi As Integer

1:      Console.WriteLine("RUMUS MATEMATIKA")
        Console.WriteLine("1. Luas persegi panjang")
        Console.WriteLine("2. Keliling persegi panjang")
        Console.WriteLine("3. Luas segitiga")
        Console.WriteLine("4. Luas lingkaran")
        Console.WriteLine("5. Keliling bujur sangkar")
        Console.ReadLine()
        Console.WriteLine()
        Console.Write("Silahkan masukan rumus yang telah disediakan : ")
        menu = Console.ReadLine()

        If menu = 1 Then
            Console.Write("Masukan panjang : ")
            a = Console.ReadLine
            Console.Write("Masukan lebar : ")
            b = Console.ReadLine

            luas = rumus(a, b)
            Console.WriteLine(menu & "." & a & "*" & b)
            Console.Write("Luas : {0}", luas)
            Console.ReadLine()
            Console.Clear()
            GoTo 1
        ElseIf menu = 2 Then
            Console.Write("Masukan nilai panjang : ")
            a = Console.ReadLine()
            Console.Write("Masukan nilai lebar : ")
            b = Console.ReadLine()

            keliling = 2 * (a + b)
            Console.WriteLine(menu & "." & "2" & (a & "+" & b))
            Console.Write("Keliling : {0}", keliling)
            Console.ReadLine()
            Console.Clear()
            GoTo 1
        ElseIf menu = 3 Then
            Console.Write("masukan alas : ")
            a = Console.ReadLine
            Console.Write("masukan tinggi : ")
            b = Console.ReadLine

            luas = rumus(a, b) / 2
            Console.Write("luas segitiga : {0}", luas)
            Console.ReadLine()
            Console.Clear()
            GoTo 1
        ElseIf menu = 4 Then
            Console.Write("masukan jari-jari : ")
            jari = Console.ReadLine

            luas = 3.14 * jari * jari
            Console.Write("luas lingkaran : {0}", luas)
            Console.ReadLine()
            Console.Clear()
            GoTo 1
        ElseIf menu = 5 Then
            Console.Write("masukan sisi : ")
            sisi = Console.ReadLine
           
            keliling = 4 * sisi
            Console.Write("keliling : {0}", keliling)
            Console.ReadLine()
            Console.Clear()
            GoTo 1
        End If

    End Sub
    Private Function rumus(ByVal panjang As Integer, ByVal lebar As Integer)
        Dim hasil As Integer

        hasil = panjang * lebar

        Return hasil
    End Function


by : 562010008@student.uksw.edu (Watashi no kantan'na memo)