Update to Go 1.9.3

Closes agones-dev#63

Author: markmandel

build/build-image/Dockerfile

@@ -22,7 +22,7 @@ RUN apt-get update && \
 
 # install go
 WORKDIR /usr/local
-ENV GO_VERSION=1.9.2
+ENV GO_VERSION=1.9.3
 ENV GOPATH /go
 RUN wget -q https://redirector.gvt1.com/edgedl/go/go${GO_VERSION}.linux-amd64.tar.gz && \
     tar -xzf go${GO_VERSION}.linux-amd64.tar.gz && rm go${GO_VERSION}.linux-amd64.tar.gz && mkdir ${GOPATH}