Sync async_nats work with master

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

gateway/Dockerfile

@@ -1,12 +1,28 @@
-FROM alpine:latest
+FROM golang:1.7.5
+WORKDIR /go/src/github.com/alexellis/faas/gateway
 
+COPY vendor         vendor
+
+COPY handlers       handlers
+COPY metrics        metrics
+COPY requests       requests
+COPY tests          tests
+
+COPY types          types
+COPY queue          queue
+COPY plugin         plugin
+COPY server.go      .
+
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o gateway .
+
+FROM alpine:latest
 WORKDIR /root/
 
 EXPOSE 8080
 ENV http_proxy      ""
 ENV https_proxy     ""
 
-COPY gateway    .
+COPY --from=0 /go/src/github.com/alexellis/faas/gateway/gateway    .
 
 COPY assets     assets