Support Retrieve file content API (#347) (#348)

* Support Retrieve file content API (#347)

* add timeout test for GetFileContent (#347)

stream.go

@@ -4,7 +4,6 @@ import (
 	"bufio"
 	"context"
 	"errors"
-	"net/http"
 
 	utils "github.com/sashabaranov/go-openai/internal"
 )
@@ -46,7 +45,7 @@ func (c *Client) CreateCompletionStream(
 	if err != nil {
 		return
 	}
-	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusBadRequest {
+	if isFailureStatusCode(resp) {
 		return nil, c.handleErrorResp(resp)
 	}