test: http test wait for http server to start (#2033)

Signed-off-by: t_max <1172915550@qq.com>

internal/io/http/httpserver/data_server_test.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"net/http"
 	"testing"
+	"time"
 
 	"github.com/lf-edge/ekuiper/internal/testx"
 )
@@ -67,11 +68,19 @@ func TestEndpoints(t *testing.T) {
 		t.Error("RegisterEndpoint should not return error for same endpoint")
 	}
 	RegisterEndpoint(endpoints[1], "PUT", "application/json")
+	// wait for http server start
+	for i := 0; i < 3; i++ {
+		err = testHttp(client, urlPrefix+endpoints[0], "POST")
+		if err == nil {
+			break
+		}
+		time.Sleep(time.Millisecond * 500)
+	}
 
-	err = testHttp(client, urlPrefix+endpoints[0], "POST")
 	if err != nil {
-		t.Error(err)
+		t.Error("httptest still fails after 3 times :", err.Error())
 	}
+
 	err = testHttp(client, urlPrefix+endpoints[1], "PUT")
 	if err != nil {
 		t.Error(err)