Problem

http.TimeoutHandler doesn't support request flushing, resulting in any flush interval set being ignored if a timeout is also set (we set a default timeout, but not flush interval, so right now this problem always occurs if a flush interval is set).

https://golang.org/src/net/http/server.go?s=98830:98898#L3129

Solution

If a flush interval is set in the upstream config, return the handler without setting a timeout.