Set ROCKET_KEEP_ALIVE=0 (#19)

Dockerfile

@@ -24,6 +24,15 @@ ENV ROCKET_LIMITS "{json=10485760}"
 # without one set Rocket emits a warning.
 ENV ROCKET_SECRET_KEY "SeerutKeyIsI7releuantAndknvsuZPluaseIgnorYA="
 
+# When keep-alive is on, we observe connection resets in our Go clients of
+# syntect_server. It is unclear why this is, especially because our Go clients do
+# not reuse the connection (i.e. we make a fresh connection every time).
+# Disabling keep-alive does resolve the issue though, our best guess is that
+# this is a bug in Hyper 0.10 (see https://github.com/SergioBenitez/Rocket/issues/928#issuecomment-464632953).
+# See https://github.com/sourcegraph/sourcegraph/issues/2615 for details on
+# what we observed when this was enabled with the default 5s.
+ENV ROCKET_KEEP_ALIVE=0
+
 RUN addgroup -S sourcegraph && adduser -S -G sourcegraph -h /home/sourcegraph sourcegraph
 USER sourcegraph