<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <script type="text/script" src="go.js"></script>
  <title>GOJS</title>
</head>
<body onload="init()">
  <div id="myDiagramDiv"></div>
  <script>
    function init() {
      if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
      var $ = go.GraphObject.make;  // for conciseness in defining templates
      myDiagram = $(go.Diagram, "myDiagramDiv",  // create a Diagram for the DIV HTML element
        {
          "undoManager.isEnabled": true  // enable undo & redo
        });
      // define a simple Node template
      myDiagram.nodeTemplate =
        $(go.Node, "Auto",  // the Shape will go around the TextBlock
          $(go.Shape, "RoundedRectangle", { strokeWidth: 0, fill: "white" },
            // Shape.fill is bound to Node.data.color
            new go.Binding("fill", "color")),
          $(go.TextBlock,
            { margin: 8, font: "bold 14px sans-serif", stroke: '#333' }, // Specify a margin to add some room around the text
            // TextBlock.text is bound to Node.data.key
            new go.Binding("text", "key"))
        );
      // but use the default Link template, by not setting Diagram.linkTemplate
      // create the model data that will be represented by Nodes and Links
      myDiagram.model = new go.GraphLinksModel(
        [
          { key: "Alpha", color: "lightblue" },
          { key: "Beta", color: "orange" },
          { key: "Gamma", color: "lightgreen" },
          { key: "Delta", color: "pink" }
        ],
        [
          { from: "Alpha", to: "Beta" },
          { from: "Alpha", to: "Gamma" },
          { from: "Beta", to: "Beta" },
          { from: "Gamma", to: "Delta" },
          { from: "Delta", to: "Alpha" }
        ]);
    }
  </script> 
</html>
I am using this code getting this error :-
Uncaught ReferenceError: go is not defined
init file:///E:/GOJSDEMO/index.html:15
onload file:///E:/GOJSDEMO/index.html:1