refactor: extract FlushWriter function for improved stream flushing

relay/channel/openai/helper.go

@@ -2,9 +2,6 @@ package openai
 
 import (
 	"encoding/json"
-	"errors"
-	"github.com/samber/lo"
-	"net/http"
 	"one-api/common"
 	"one-api/dto"
 	"one-api/logger"
@@ -15,6 +12,8 @@ import (
 	"one-api/types"
 	"strings"
 
+	"github.com/samber/lo"
+
 	"github.com/gin-gonic/gin"
 )
 
@@ -71,11 +70,7 @@ func handleGeminiFormat(c *gin.Context, data string, info *relaycommon.RelayInfo
 
 	// send gemini format response
 	c.Render(-1, common.CustomEvent{Data: "data: " + string(geminiResponseStr)})
-	if flusher, ok := c.Writer.(http.Flusher); ok {
-		flusher.Flush()
-	} else {
-		return errors.New("streaming error: flusher not found")
-	}
+	_ = helper.FlushWriter(c)
 	return nil
 }
 
@@ -253,9 +248,7 @@ func HandleFinalResponse(c *gin.Context, info *relaycommon.RelayInfo, lastStream
 
 		// 发送最终的 Gemini 响应
 		c.Render(-1, common.CustomEvent{Data: "data: " + string(geminiResponseStr)})
-		if flusher, ok := c.Writer.(http.Flusher); ok {
-			flusher.Flush()
-		}
+		_ = helper.FlushWriter(c)
 	}
 }