框架自身不带任何监控打点，只是提供了 Tracer 接口，用户可以根据需求实现该接口，并通过 WithTracer Option 来注入。
// Tracer is executed at the start and finish of an RPC.
type Tracer interface {
Start(ctx context.Context) context.Context
Finish(ctx context.Context)
}kitex-contrib 中提供了 prometheus 的监控扩展，使用方式：
Client
import (
"github.com/kitex-contrib/prometheus"
kClient "github.com/cloudwego/kitex/client"
)
...
client, _ := testClient.NewClient(
"DestServiceName",
kClient.WithTracer(prometheus.NewClientTracer(":9091", "/kitexclient")))
resp, _ := client.Send(ctx, req)
...Server
import (
"github.com/kitex-contrib/prometheus"
kServer "github.com/cloudwego/kitex/server"
)
func main() {
...
svr := xxxservice.NewServer(
&myServiceImpl{},
kServer.WithTracer(prometheus.NewServerTracer(":9092", "/kitexserver")))
svr.Run()
...
}