How to use the @opentelemetry/core.initGlobalTracer function in @opentelemetry/core

let exporter;
  if (EXPORTER.toLowerCase().startsWith('z')) {
    exporter = new ZipkinExporter({
      serviceName: service,
    });
  } else {
    exporter = new JaegerExporter({
      serviceName: service,
    });
  }

  tracer.addSpanProcessor(new SimpleSpanProcessor(exporter));

  // Initialize the OpenTelemetry APIs to use the BasicTracer bindings
  opentelemetry.initGlobalTracer(tracer);
}

const tracer = new NodeTracer();

  if (EXPORTER.toLowerCase().startsWith('z')) {
    exporter = new ZipkinExporter({
      serviceName: service
    });
  } else {
    exporter = new JaegerExporter({
      serviceName: service,
    });
  }

  tracer.addSpanProcessor(new SimpleSpanProcessor(exporter));

  // Initialize the OpenTelemetry APIs to use the BasicTracer bindings
  opentelemetry.initGlobalTracer(tracer);
}

const EXPORTER = process.env.EXPORTER || '';
if (EXPORTER.toLowerCase().startsWith('z')) {
  exporter = new ZipkinExporter(options);
} else if (EXPORTER.toLowerCase().startsWith('j')) {
  exporter = new JaegerExporter(options);
} else {
  exporter = new CollectorExporter(options);
}

const tracer = new BasicTracer();

// Configure span processor to send spans to the provided exporter
tracer.addSpanProcessor(new SimpleSpanProcessor(exporter));

// Initialize the OpenTelemetry APIs to use the BasicTracer bindings
opentelemetry.initGlobalTracer(tracer);

// Create a span. A span must be closed.
const span = opentelemetry.getTracer().startSpan('main');
for (let i = 0; i < 10; i++) {
  doWork(span);
}
// Be sure to end the span.
span.end();

// flush and close the connection.
exporter.shutdown();

function doWork(parent) {
  // Start another span. In this example, the main method already started a
  // span, so that'll be the parent span, and this will be a child span.
  const span = opentelemetry.getTracer().startSpan('doWork', {

http: {
        enabled: true,
        path: "@opentelemetry/plugin-http"
      }
    }
  });

  tracer.addSpanProcessor(new SimpleSpanProcessor(new ZipkinExporter({
    serviceName: service,
  })));
  tracer.addSpanProcessor(new SimpleSpanProcessor(new JaegerExporter({
    serviceName: service,
  })));

  // Initialize the OpenTelemetry APIs to use the BasicTracer bindings
  opentelemetry.initGlobalTracer(tracer);
}

let exporter;
  if (EXPORTER.toLowerCase().startsWith('z')) {
    exporter = new ZipkinExporter({
      serviceName: service,
    });
  } else {
    exporter = new JaegerExporter({
      serviceName: service,
    });
  }

  tracer.addSpanProcessor(new SimpleSpanProcessor(exporter));

  // Initialize the OpenTelemetry APIs to use the BasicTracer bindings
  opentelemetry.initGlobalTracer(tracer);
}

let exporter;
  if (EXPORTER.toLowerCase().startsWith('z')) {
    exporter = new ZipkinExporter({
      serviceName: service,
    });
  } else {
    exporter = new JaegerExporter({
      serviceName: service,
    });
  }

  tracer.addSpanProcessor(new SimpleSpanProcessor(exporter));

  // Initialize the OpenTelemetry APIs to use the BasicTracer bindings
  opentelemetry.initGlobalTracer(tracer);
}

const collectorExporter = new CollectorExporter({serviceName: 'basic-service'});

// It is recommended to use this BatchSpanProcessor for better performance
// and optimization, especially in production.
tracer.addSpanProcessor(new BatchSpanProcessor(zipkinExporter, {
  bufferSize: 10 // This is added for example, default size is 100.
}));

// It is recommended to use SimpleSpanProcessor in case of Jaeger exporter as
// it's internal client already handles the spans with batching logic.
tracer.addSpanProcessor(new SimpleSpanProcessor(jaegerExporter));

tracer.addSpanProcessor(new SimpleSpanProcessor(collectorExporter));

// Initialize the OpenTelemetry APIs to use the BasicTracer bindings
opentelemetry.initGlobalTracer(tracer);

// Create a span. A span must be closed.
const span = opentelemetry.getTracer().startSpan('main');
for (let i = 0; i < 10; i++) {
  doWork(span);
}
// Be sure to end the span.
span.end();

// flush and close the connection.
zipkinExporter.shutdown();
jaegerExporter.shutdown();
collectorExporter.shutdown();

function doWork(parent) {
  // Start another span. In this example, the main method already started a