func getFShader2() string {
	fs := `
	   #version 410
	   out vec4 frag_colour;
	   void main() {
	       frag_colour = vec4(0.5, 1, 1, 1);
	   }
	` + "\x00"
	return fs
}
func compileShader(source string, shaderType uint32) (uint32, error) {
	shader := gl.CreateShader(shaderType)

	csources, free := gl.Strs(source)
	gl.ShaderSource(shader, 1, csources, nil)
	free()
	gl.CompileShader(shader)

	var status int32
	gl.GetShaderiv(shader, gl.COMPILE_STATUS, &status)
	if status == gl.FALSE {
		var logLength int32
		gl.GetShaderiv(shader, gl.INFO_LOG_LENGTH, &logLength)

		log := strings.Repeat("\x00", int(logLength+1))
		gl.GetShaderInfoLog(shader, logLength, nil, gl.Str(log))

		return 0, fmt.Errorf("failed to compile %v: %v", source, log)
	}

	return shader, nil
}
...
	vs := getVShader()
	fs := getFShader()
	fs2 := getFShader2()
	if err := gl.Init(); err != nil {
		panic(err)
	}
	vertexShader, err := compileShader(vs, gl.VERTEX_SHADER)
	if err != nil {
		panic(err)
	}
	fragmentShader, err := compileShader(fs, gl.FRAGMENT_SHADER)
	if err != nil {
		panic(err)
	}

	prog := gl.CreateProgram()
	gl.AttachShader(prog, vertexShader)
	gl.AttachShader(prog, fragmentShader)
	gl.LinkProgram(prog)

	prog2 := gl.CreateProgram()
	gl.AttachShader(prog2, vertexShader)
	gl.AttachShader(prog2, fragmentShader2)
	gl.LinkProgram(prog2)
	
...
		gl.UseProgram(prog2)
		gl.BindVertexArray(VAO2)
		gl.DrawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, nil)
		gl.BindVertexArray(0)
		
...