Manually reset the buffer when streaming request body (#2183)

sanic/http.py

@@ -490,6 +490,9 @@ class Http:
 
             if size <= 0:
                 self.request_body = None
+                # Because we are leaving one CRLF in the buffer, we manually
+                # reset the buffer here
+                self.recv_buffer = bytearray()
 
                 if size < 0:
                     self.keep_alive = False