How to set/get protobuf's extension field in Go?

I am a Go language developer. Our team chose to use protocol buffers to transform data.
I chose this protobuf package: https://github.com/golang/protobuf.
However, this package has no method to handle the extensions field in a protocol buffer. I have only found this code in the class file generated by protoc:

<!-- language: go -->

var E_Height = &proto.ExtensionDesc{
	ExtendedType:  (*Person)(nil),
	ExtensionType: (*int32)(nil),
	Field:         110,
	Name:          "eg.Height",
	Tag:           "varint,110,opt",
}

func init() {
	proto.RegisterExtension(E_Height)
}

So, how can I set/get the extensions field in Go?

Getting the extension...

yourExtendedEvent := &path_to_your_events.Person{}
err := proto.Unmarshal(yourBytes, yourExtendedEvent)
if err != nil {
    // handle error case
}
extendedEvent, extendedError := proto.GetExtension(
    yourExtendedEvent,
    path_to_your_events.E_Height,
)
...

Setting the extension...

yourExtendedEvent := &path_to_your_events.Person{
    Field1: proto.Uint64(1),
    Field2: proto.String("foo"),
}

height := &path_to_your_events.Height {
    Field1: proto.Int64(120),
}

err := proto.SetExtension(
    yourExtendedEvent,
    path_to_your_events.E_Height,
    height,
)

if err != nil {
    // handle error case
}

EDIT

Actually, if I am reading it right, your extension is just a single field (an int32) so I don't know that you actually have a Height type. If not, it might be more like

height := proto.Int32(120)

And then you set the same way with height as a single field rather than as a distinct proto type.

This line

ExtensionType: (*int32)(nil),

Makes me think it will be a single field, whereas our extensions look more like

ExtensionType: (*SomeOtherType)(nil),

This is a good resource
TestExtensionsRoundTrip

From: https://developers.google.com/protocol-buffers/docs/reference/go-generated#extensions

> For example, given the following definition:
>
>
> extend Foo {
> optional int32 singular_int32 = 1;
> repeated bytes repeated_string = 2;
> optional Bar repeated_message = 3;
> }
>
>
> Extension values may be accessed as:
>
>
> m := &somepb.Foo{}
> proto.SetExtension(m, extpb.E_SingularInt32, int32(1))
> proto.SetExtension(m, extpb.E_RepeatedString, []string{"a", "b", "c"})
> proto.SetExtension(m, extpb.E_RepeatedMessage, &extpb.Bar{})
>
> v1 := proto.GetExtension(m, extpb.E_SingularInt32).(int32)
> v2 := proto.GetExtension(m, extpb.E_RepeatedString).([][]byte)
> v3 := proto.GetExtension(m, extpb.E_RepeatedMessage).(*extpb.Bar)
>