这里有一个例子，同时回答了（1）和（2）。

package main

import (
    "context"
    "fmt"
    "log"
    "time"

    "go.opentelemetry.io/otel"
    "go.opentelemetry.io/otel/attribute"
    "go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
    "go.opentelemetry.io/otel/sdk/resource"
    sdktrace "go.opentelemetry.io/otel/sdk/trace"
    "go.opentelemetry.io/otel/trace"
)

func main() {
    // Create a trace provider with a custom exporter (e.g., stdout exporter for testing)
    exporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
    if err != nil {
        log.Fatalf("Error creating exporter: %v", err)
    }
    resources, err := resource.New(
        context.Background(),
        resource.WithAttributes(
            attribute.String("service.name", "serviceName"),
            attribute.String("library.language", "go"),
        ),
    )
    tp := sdktrace.NewTracerProvider(
        sdktrace.WithBatcher(exporter),
        sdktrace.WithResource(resources),
    )
    otel.SetTracerProvider(tp)

    // Manually create a custom TraceID and SpanID for the root span
    traceID := trace.TraceID([16]byte{0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10})
    spanID := trace.SpanID([8]byte{0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77})

    ctx := trace.ContextWithRemoteSpanContext(
        context.Background(),
        trace.NewSpanContext(trace.SpanContextConfig{
            TraceID:    traceID,
            SpanID:     spanID,
            TraceFlags: trace.FlagsSampled,
        }),
    )

    // Create and start the root span with the custom TraceID and SpanID
    tracer := otel.GetTracerProvider().Tracer("my-tracer")
    _, rootSpan := tracer.Start(ctx, "root-span")
    defer rootSpan.End()

    // Your code here
    fmt.Println("Hello from root span!")
    createChildSpan(ctx)
    time.Sleep(10*time.Second)
}

// In another part of your code or a different process, you can create child spans
// referencing the custom root span created in step 1.

func createChildSpan(ctx context.Context) {
    tracer := otel.GetTracerProvider().Tracer("my-tracer")
    _, childSpan := tracer.Start(ctx, "child-span")
    defer childSpan.End()

    // Your code here
    fmt.Println("Hello from child span!")
}