don't fire ErrServerClosed on manually interrupt signals (CTRL/CMD+C)

Former-commit-id: 673c84dd13bb99c0926aa1b4a6b4eff9745403d8

_examples/http_responsewriter/sse-third-party/main.go

@@ -44,7 +44,7 @@ func main() {
 		})
 	}() // ...
 
-	app.Listen(":8080", iris.WithoutServerError(iris.ErrServerClosed))
+	app.Listen(":8080")
 }
 
 /* For a golang SSE client you can look at: https://github.com/r3labs/sse#example-client */