var tracer = otel.Tracer("go-moda")
func InitJaegerProvider(jaegerUrl string, serviceName string) (func(ctx context.Context) error, error) {
    if jaegerUrl == "" {
        logger.Errorw("jaeger url is empty")
        return nil, nil
    }
    tracer = otel.Tracer(serviceName)
    exp, err := jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(jaegerUrl)))
    if err != nil {
        return nil, err
    }
    tp := tracesdk.NewTracerProvider(
        tracesdk.WithBatcher(exp),
        tracesdk.WithResource(resource.NewSchemaless(
            semconv.ServiceNameKey.String(serviceName),
        )),
    )
    otel.SetTracerProvider(tp)
    // otel.SetTextMapPropagator(propagation.TraceContext{})
    b3Propagator := b3.New(b3.WithInjectEncoding(b3.B3MultipleHeader))
    propagator := propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}, b3Propagator)
    otel.SetTextMapPropagator(propagator)
    return tp.Shutdown, nil
}

ctx, span := tracing.Start(ctx, "service.bar")
defer span.End()

import "go.opentelemetry.io/contrib/instrumentation/github.com/labstack/echo/otelecho"
e := echo.New()
e.Server.Use(otelecho.Middleware("moda"))

import "go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
ginEngine := gin.Default()
g.GetServer().Use(otelgin.Middleware("my-server"))

package tracing
import (
    "bytes"
    "context"
    "encoding/json"
    "io"
    "io/ioutil"
    "net/http"
    "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
)
// 新增 options  http.Transport
type ClientOption struct {
    Transport *http.Transport
}
type ClientOptionFunc func(*ClientOption)
func WithClientTransport(transport *http.Transport) ClientOptionFunc {
    return func(option *ClientOption) {
        option.Transport = transport
    }
}
// CallAPI 為 http client 封裝,默認(rèn)使用 otelhttp.NewTransport(http.DefaultTransport)
func CallAPI(ctx context.Context, url string, method string, reqBody interface{}, option ...ClientOptionFunc) ([]byte, error) {
    clientOption := &ClientOption{}
    for _, o := range option {
        o(clientOption)
    }
    client := http.Client{Transport: otelhttp.NewTransport(http.DefaultTransport)}
    if clientOption.Transport != nil {
        client.Transport = otelhttp.NewTransport(clientOption.Transport)
    }
    var requestBody io.Reader
    if reqBody != nil {
        payload, err := json.Marshal(reqBody)
        if err != nil {
            return nil, err
        }
        requestBody = bytes.NewReader(payload)
    }
    req, err := http.NewRequestWithContext(ctx, method, url, requestBody)
    if err != nil {
        return nil, err
    }
    resp, err := client.Do(req)
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()
    resBody, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        return nil, err
    }
    return resBody, nil
}