Highcharts-ng add a custom button to speedometer - angularjs

Question

I am working with angularjs highcharts-ng
https://github.com/pablojim/highcharts-ng
I need to add a custom button to the speedometer.
I've found this:
Add buttons in chart of Highcharts at runtime
exporting: {
buttons: {
customButton: {
text: 'Custom Button',
onclick: function () {
alert('You pressed the button!');
}
}
}
}
But it is not working to me:
$scope.highchartsNG = {
options: {
chart: {
type: 'gauge',
plotBackgroundColor: null,
plotBackgroundImage: null,
plotBorderWidth: 0,
plotShadow: false
},
title: {
text: 'Speedometer'
},
pane: {
startAngle: -150,
endAngle: 150,
background: [{
backgroundColor: {
linearGradient: {
x1: 0,
y1: 0,
x2: 0,
y2: 1
},
stops: [
[0, '#FFF'],
[1, '#333']
]
},
borderWidth: 0,
outerRadius: '109%'
}, {
backgroundColor: {
linearGradient: {
x1: 0,
y1: 0,
x2: 0,
y2: 1
},
stops: [
[0, '#333'],
[1, '#FFF']
]
},
borderWidth: 1,
outerRadius: '107%'
}, {
// default background
}, {
backgroundColor: '#DDD',
borderWidth: 0,
outerRadius: '105%',
innerRadius: '103%'
}]
}
},
exporting: {
buttons: {
customButton: {
text: 'Custom Button',
onclick: function () {
alert('You pressed the button!');
}
}
}
},
yAxis: {
min: 0,
max: 200,
minorTickInterval: 'auto',
minorTickWidth: 1,
minorTickLength: 10,
minorTickPosition: 'inside',
minorTickColor: '#666',
tickPixelInterval: 30,
tickWidth: 2,
tickPosition: 'inside',
tickLength: 10,
tickColor: '#666',
labels: {
step: 2,
rotation: 'auto'
},
title: {
text: 'km/h'
},
plotBands: [{
from: 0,
to: 120,
color: '#55BF3B' // green
}, {
from: 120,
to: 160,
color: '#DDDF0D' // yellow
}, {
from: 160,
to: 200,
color: '#DF5353' // red
}]
},
buttons: {
customButton: {
text: 'Custom Button'
}
}
,
series: [{
name: 'Speed',
data: [80],
tooltip: {
valueSuffix: ' km/h'
}
}],
};
http://jsfiddle.net/76dLm8h7/3/
I've tried to add the "exporting" option in different possitions inside the array, but It does'nt work.
Any help will be appreciate.
Thanks in advance.