This Doesn't Work

package main

import (
    "fmt"
    "github.com/BurntSushi/xgb"
    "github.com/BurntSushi/xgb/xproto"
    "github.com/Joker/go-cairo"
)

type XConn struct {
    *xgb.Conn
}

func NewXConn () (*XConn, error) {
    this := new (XConn)
    var err error
    this.Conn, err = xgb.NewConn ()
    if err != nil { this.Conn = nil }
    return this, err
}

func (this *XConn) SetupInfo () *xproto.SetupInfo {
    return xproto.Setup (this.Conn)
}

func (this *XConn) DefaultScreen () *xproto.ScreenInfo {
    setup := this.SetupInfo ()
    return setup.DefaultScreen (this.Conn)
}

func (this *XConn) Surface (x, y int16, width, height, border uint16) *cairo.Surface {
    wid, _ := xproto.NewWindowId (this.Conn)

    screen := this.DefaultScreen ()

    structureNotify := xproto.EventMaskStructureNotify
    keyPress := xproto.EventMaskKeyPress
    keyRelease := xproto.EventMaskKeyRelease

    masks := uint32 (structureNotify | keyPress | keyRelease)
    valList := []uint32 {0xffffffff, masks}

    xproto.CreateWindow ( this.Conn,                                                                // connection
        screen.RootDepth,                                                   // depth
        wid,                                                                            // window id
        screen.Root,                                                            // parent
        x, y, width, height, border,
        xproto.WindowClassInputOutput,                      // class
        screen.RootVisual,                                              // visual
        xproto.CwBackPixel | xproto.CwEventMask,    // value mask
        valList)                                                                        // value list
    xproto.MapWindow (this.Conn, wid)

    drawable := xproto.Drawable (wid)
    visualInfo := screen.AllowedDepths[0].Visuals[0]
    surface := cairo.NewSurfaceFromXCB (drawable, visualInfo, int (width), int(height))
    surface.Scale (float64 (width), float64(height))

    return surface
}

func Setup () (*XConn, error) {
    X, err := NewXConn ()
    if err != nil { return nil, err }
    surface := X.Surface (0, 0, 240, 240, 0)

    /* Drawing code goes here */
    surface.SetSourceRGB (1.0, 1.0, 1.0)

    /* baseline, descent, ascent, height */
    surface.SetLineWidth (4)
    surface.Rectangle (0, 0, 240, 240)
    surface.Stroke();
    surface.Paint();

    /* extents: width & height */
    surface.Rectangle (0, 0, 100, 100)
    surface.Stroke();

    /* text's advance */
    surface.SetSourceRGBA(0, 0, 0.75, 0.5);
    surface.Fill();

    surface.Finish()
    surface.Destroy()

    return X, nil
}

func main () {
    X, err := Setup ()
    if err != nil { fmt.Println (err) }
    for {
        ev, xerr := X.WaitForEvent()
        if ev == nil && xerr == nil {
            fmt.Println("Both event and error are nil. Exiting...")
            return
        }

        if ev != nil {
            fmt.Printf("Event: %s\n", ev)
        }
        if xerr != nil {
            fmt.Printf("Error: %s\n", xerr)
        }
    }
}