Node.js gRPC client -> Go gRPC server

geoip_client.js

const apm = require('elastic-apm-node').start({
        serviceName: 'geoip-node-client'
});

var grpc = require('grpc');
var interceptor = function(options, nextCall) {
        return new grpc.InterceptingCall(nextCall(options), {
                start: function(metadata, listener, next) {
                        var span = apm.startSpan('grpc');
                        var traceparent = span._context.toString();
                        metadata.add('elastic-apm-traceparent', traceparent);
                        console.log("metadata:", metadata);
                        next(metadata, listener, next);
                        span.end();
                }
        });
}

var PROTO_PATH = __dirname + '/proto/geoip/geoip.proto';
var protoLoader = require('@grpc/proto-loader');
var packageDefinition = protoLoader.loadSync(
    PROTO_PATH,
    {keepCase: true,
     longs: String,
     enums: String,
     defaults: true,
     oneofs: true
    });
var geoip = grpc.loadPackageDefinition(packageDefinition).geoip;
var options = {interceptors: [interceptor]};
var client = new geoip.Geoip('localhost:8008', grpc.credentials.createInsecure(), options);

var trans = apm.startTransaction('client_request', 'custom');
var ip = Buffer.from([124, 148, 74, 92]);
client.Lookup({IP: ip}, function(err, result) {
        console.log(err, result);
});
trans.end();
apm.flush();