feat: support pipe function for stream

README.md

@@ -821,6 +821,18 @@ c := cod.NewContext(resp, req)
 c.DisableReuse()
 ```
 
+### Pipe
+
+将当前Reader pipe向Response，用于流式输出响应数据，节省内存。
+
+```go
+resp := httptest.NewRecorder()
+c := NewContext(resp, nil)
+data := []byte("abcd")
+r := bytes.NewReader(data)
+c.Pipe(r)
+```
+
 ## Group
 
 ### NewGroup 

context.go

@@ -17,6 +17,7 @@ package cod
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"mime"
 	"net"
 	"net/http"
@@ -436,6 +437,12 @@ func (c *Context) Pass(another *Cod) {
 	another.ServeHTTP(c.Response, c.Request)
 }
 
+// Pipe pie to the response
+func (c *Context) Pipe(r io.Reader) (written int64, err error) {
+	c.Committed = true
+	return io.Copy(c.Response, r)
+}
+
 // NewContext new a context
 func NewContext(resp http.ResponseWriter, req *http.Request) *Context {
 	c := &Context{}

context_test.go

@@ -466,10 +466,23 @@ func TestContextPass(t *testing.T) {
 	resp := httptest.NewRecorder()
 	d.GET("/", func(c *Context) error {
 		c.Pass(another)
+		// the data will be ignored
 		c.BodyBuffer = bytes.NewBufferString("original data")
 		return nil
 	})
 	d.ServeHTTP(resp, req)
 	assert.Equal(resp.Code, 200)
 	assert.Equal(resp.Body.String(), "new data")
 }
+
+func TestPipe(t *testing.T) {
+	assert := assert.New(t)
+	resp := httptest.NewRecorder()
+	c := NewContext(resp, nil)
+	data := []byte("abcd")
+	r := bytes.NewReader(data)
+	written, err := c.Pipe(r)
+	assert.Nil(err)
+	assert.Equal(written, int64(len(data)))
+	assert.Equal(data, resp.Body.Bytes())
+}