fix: set Accept header if not given (#615)

* fix: fastgpt调用通义千问问答失败

* refactor: Dockerfile

* Revert "refactor: Dockerfile"

This reverts commit a538c4f28e.

* chore: update implementation

---------

Co-authored-by: JustSong <songquanpeng@foxmail.com>

controller/relay-text.go

@@ -6,13 +6,14 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"github.com/gin-gonic/gin"
 	"io"
 	"net/http"
 	"one-api/common"
 	"one-api/model"
 	"strings"
 	"time"
+
+	"github.com/gin-gonic/gin"
 )
 
 const (
@@ -361,6 +362,9 @@ func relayTextHelper(c *gin.Context, relayMode int) *OpenAIErrorWithStatusCode {
 		}
 		req.Header.Set("Content-Type", c.Request.Header.Get("Content-Type"))
 		req.Header.Set("Accept", c.Request.Header.Get("Accept"))
+		if isStream && c.Request.Header.Get("Accept") == "" {
+			req.Header.Set("Accept", "text/event-stream")
+		}
 		//req.Header.Set("Connection", c.Request.Header.Get("Connection"))
 		resp, err = httpClient.Do(req)
 		if err != nil {