func (c *Controller) Append(col stats.Tracer) {
	c.tracers = append(c.tracers, col)
}
Append appends a new tracer to the controller.
package stats
import (
	"context"
	"runtime/debug"
	"github.com/cloudwego/kitex/pkg/klog"
	"github.com/cloudwego/kitex/pkg/rpcinfo"
	"github.com/cloudwego/kitex/pkg/stats"
)
type Controller struct {
	tracers []stats.Tracer
}