add eof method to close stream (#2094)

* add eof method to close stream

* Add eof test

Co-authored-by: Ajay Gupta <ajay.gupta@1mg.com>
Co-authored-by: Adam Hopkins <admhpkns@gmail.com>

sanic/response.py

@@ -203,6 +203,9 @@ class StreamingHTTPResponse(BaseHTTPResponse):
             self.streaming_fn = None
         await super().send(*args, **kwargs)
 
+    async def eof(self):
+        raise NotImplementedError
+
 
 class HTTPResponse(BaseHTTPResponse):
     """
@@ -235,6 +238,9 @@ class HTTPResponse(BaseHTTPResponse):
         self.headers = Header(headers or {})
         self._cookies = None
 
+    async def eof(self):
+        await self.send("", True)
+
 
 def empty(
     status=204, headers: Optional[Dict[str, str]] = None