fix:修复demo中缺失import问题

examples/quickstart/provider/main.go

@@ -27,7 +27,6 @@ import (
 	"os/signal"
 	"strings"
 	"syscall"
-	"time"
 
 	"github.com/polarismesh/polaris-go"
 )
@@ -123,22 +122,6 @@ func (svr *PolarisProvider) deregisterService() {
 	log.Printf("deregister successfully.")
 }
 
-func (svr *PolarisProvider) doHeartbeat() {
-	log.Printf("start to invoke heartbeat operation")
-	ticker := time.NewTicker(time.Duration(5 * time.Second))
-	for range ticker.C {
-		if !svr.isShutdown {
-			heartbeatRequest := &polaris.InstanceHeartbeatRequest{}
-			heartbeatRequest.Namespace = namespace
-			heartbeatRequest.Service = service
-			heartbeatRequest.Host = svr.host
-			heartbeatRequest.Port = svr.port
-			heartbeatRequest.ServiceToken = token
-			svr.provider.Heartbeat(heartbeatRequest)
-		}
-	}
-}
-
 func (svr *PolarisProvider) runMainLoop() {
 	ch := make(chan os.Signal, 1)
 	signal.Notify(ch, []os.Signal{