Add files via upload

internal/handler/sse_keepalive.go

@@ -0,0 +1,38 @@
+package handler
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+// sseKeepalive sends periodic SSE comment lines so proxies (e.g. nginx proxy_read_timeout)
+// and idle TCP paths do not close long-running streams when no data events are emitted for a while.
+func sseKeepalive(c *gin.Context, stop <-chan struct{}) {
+	ticker := time.NewTicker(20 * time.Second)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-stop:
+			return
+		case <-c.Request.Context().Done():
+			return
+		case <-ticker.C:
+			select {
+			case <-stop:
+				return
+			case <-c.Request.Context().Done():
+				return
+			default:
+			}
+			if _, err := fmt.Fprintf(c.Writer, ": keepalive\n\n"); err != nil {
+				return
+			}
+			if flusher, ok := c.Writer.(http.Flusher); ok {
+				flusher.Flush()
+			}
+		}
+	}
+}