VB.Net - GoTo语句

Module loops
   Sub Main()
      ' local variable definition 
      Dim a As Integer = 10
Line1:
      Do
          If (a = 15) Then
              ' skip the iteration '
              a = a + 1
              GoTo Line1
          End If
          Console.WriteLine("value of a: {0}", a)
          a = a + 1
      Loop While (a < 20)
      Console.ReadLine()
   End Sub
End Module

value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 16
value of a: 17
value of a: 18
value of a: 19