Issue: Parsing (Unmarshal) ALBTargetGroupRequest request body triggered by ALB with gRPC

I'm trying to parse the request body from the `events.ALBTargetGroupRequest` in my lambda function.

I couldn't find any example or explanation on how should I parse this binary data. My thought was that I would get a proto and just Unmarshal it, but that's not the case.
The flow is **gRPC-->ALB-->Lambda**.

Lambda Code Example:
``` go
func HandleRequest(ctx context.Context, request events.ALBTargetGroupRequest) (events.ALBTargetGroupResponse, error) {
bt, err := base64.StdEncoding.DecodeString(request.Body)
if err != nil {
log.Printf("Failed to decode body: %s\n", err.Error())
return events.ALBTargetGroupResponse{}, err
}

msg := pb.Msg{}
err = proto.Unmarshal(bt, &msg)
if err != nil {
log.Printf("Failed to unmarshal body: %s\n", err.Error())
return events.ALBTargetGroupResponse{}, err
}

return events.ALBTargetGroupResponse{Body: "", StatusCode: 200, StatusDescription: "200 OK", IsBase64Encoded: false, Headers: map[string]string{}}, nil
}

func main() {
lambda.Start(HandleRequest)
}
```

Headers:
```json
{
"accept-encoding": "identity,gzip",
"content-type": "application/grpc",
"grpc-accept-encoding": "identity,deflate,gzip",
"grpc-timeout": "353S",
"te": "trailers",
"user-agent": "grpc-c++/1.16.0 grpc-c/6.0.0 (linux; chttp2; gao)",
"x-amzn-trace-id": "Root=1-6124edf6-4fa33c5674127c7266ba0430"
}
```
Error:
```
Failed to Unmarshal body: proto: cannot parse invalid wire-format data
proto: cannot parse invalid wire-format data: prefixError
```
Byte array: (if it helps)
```
[0 0 0 12 70 10 195 24 123 32 ....]
```

I would appreciate if someone can shed some light on this subject.