Support for http.Flusher in Vercel's Serverless Environment

[leafmoes]

I am trying to implement Server-Sent Events (SSE) in my Go application deployed on Vercel. However, I encountered an issue where the ResponseWriter provided by Vercel’s bridge does not implement the http.Flusher interface. This prevents me from using the Flush() method to send data to the client in real-time.

Here is the error message I received:

interface conversion: *bridge.ResponseWriter is not http.Flusher: missing method Flush

This limitation makes it impossible to achieve true streaming behavior (e.g., SSE or chunked responses) in Vercel’s serverless environment. While I understand that Vercel’s architecture is optimized for buffered responses, supporting http.Flusher would enable developers to build real-time applications like chatbots, live updates, and more.

Request:

1. Could you consider adding support for http.Flusher in Vercel’s bridge.ResponseWriter?
2. Alternatively, could you provide guidance on how to achieve real-time streaming in Vercel’s environment?

Thank you for your attention to this matter. I look forward to your response.

[swarnava (Swarnava Sengupta)]

You’re encountering a common limitation with Go serverless functions on Vercel. The Go runtime on Vercel doesn’t currently support the http.Flusher interface in its ResponseWriter implementation, which prevents true streaming responses like Server-Sent Events (SSE).

You need to use python or node runtime to use streaming.