fix #1669 write empty body panic error

context/context.go

@@ -24,11 +24,13 @@ package context
 
 import (
 	"bufio"
+	"bytes"
 	"crypto/hmac"
 	"crypto/sha1"
 	"encoding/base64"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"strconv"
@@ -184,6 +186,14 @@ func (w *Response) Write(p []byte) (int, error) {
 	return w.ResponseWriter.Write(p)
 }
 
+// Write writes the data to the connection as part of an HTTP reply,
+// and sets `started` to true.
+// started means the response has sent out.
+func (w *Response) Copy(buf *bytes.Buffer) (int64, error) {
+	w.Started = true
+	return io.Copy(w.ResponseWriter, buf)
+}
+
 // WriteHeader sends an HTTP response header with status code,
 // and sets `started` to true.
 func (w *Response) WriteHeader(code int) {