Document that Close must be called on the reader returned from NewStreamReader

stream.go

@@ -21,8 +21,11 @@ type StreamWriter func(w *bufio.Writer)
 //
 // The returned reader may be passed to Response.SetBodyStream.
 //
+// Close must be called on the returned reader after after all the required data
+// has been read. Otherwise goroutine leak may occur.
+//
 // See also Response.SetBodyStreamWriter.
-func NewStreamReader(sw StreamWriter) io.Reader {
+func NewStreamReader(sw StreamWriter) io.ReadCloser {
 	pr, pw := io.Pipe()
 
 	var bw *bufio.Writer