Fn function terminates before timeout - fn

Question

I have set the timeout in func.yaml to 300 seconds (5 minutes) but the function only runs for 2 minutes and then terminates with error code 502.
Error invoking function. status: 502 message: error receiving function response
There is a github issue that discusses this problem:
https://github.com/fnproject/fn/issues/723
How do I resolve this problem?
Edit:
As an example, I created a nodejs function which should respond after 270 seconds but doesn't due to early timeout.
fdk.handle(function(input){
return new Promise((resolve,reject)=>{
setTimeout(()=>resolve("Hello"),270000);
});
})