import (
    "context"
    "log"

    "go.opencensus.io/trace"
    "go.opencensus.io/trace/propagation"
)

func main() {
    ctx := context.Background()

    // 创建跟踪器和 span
    _, span := trace.StartSpan(ctx, "my-trace")
    defer span.End()

    // 记录一个事件
    span.AddEvent("my-event")

    // 获取当前 span
    sp := trace.FromContext(ctx)
    log.Printf("当前 span id: %s, trace id: %s", sp.SpanID(), sp.TraceID())

    // Propagate the trace context
    prop := propagation.HTTPFormat{}
    header := prop.FormatHeader(sp.Context())
    log.Printf("Propagated header: %s", header)
}

import (
    "context"
    "log"
    "net/http"

    "go.opencensus.io/trace"
    "go.opencensus.io/trace/propagation"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        ctx := r.Context()

        // 开始一个 span
        ctx, span := trace.StartSpan(ctx, "my-http-trace")
        defer span.End()

        // 记录一个事件
        span.AddEvent("received-http-request")

        // 在分析请求中 trace 头
        prop := propagation.HTTPFormat{}
        ctx, err := prop.Extract(r, trace.FormatGrpc)
        if err != nil {
            log.Fatal(err)
        }
        sp = trace.FromContext(ctx)

        log.Printf("当前 span id: %s, trace id: %s", sp.SpanID(), sp.TraceID())
    })

    log.Fatal(http.ListenAndServe(":8080", nil))
}