CIAB: set GOPROXY to use go module mirror for CentOS 7 (#6534)

On CentOS 7, the available version of git and/or go is too old and has
an issue when running `go get`:

    git fetch-pack: expected shallow list

By setting GOPROXY, git isn't required for `go get` and solves this
issue. See golang/go#38373 for more details.

Author: rawlinp

CHANGELOG.md

@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 ## [unreleased]
 ### Fixed
 - Update traffic_portal dependencies to mitigate `npm audit` issues.
+- Fixed a cdn-in-a-box build issue when using `RHEL_VERSION=7`
 
 ### Removed
 - Remove traffic_portal dependencies to mitigate `npm audit` issues, specifically `grunt-concurrent`, `grunt-contrib-concat`, `grunt-contrib-cssmin`, `grunt-contrib-jsmin`, `grunt-contrib-uglify`, `grunt-contrib-htmlmin`, `grunt-newer`, and `grunt-wiredep`

infrastructure/cdn-in-a-box/cache/Dockerfile

@@ -117,7 +117,7 @@ CMD /run.sh
 
 FROM common-traffic-server-dependencies AS get-delve
 RUN dnf -y install golang && \
-    go get -u github.com/go-delve/delve/cmd/dlv
+    GOPROXY='https://proxy.golang.org' go get -u github.com/go-delve/delve/cmd/dlv
 
 FROM common-cache-config-layers AS mid
 ENV CACHE_TYPE=mid

infrastructure/cdn-in-a-box/traffic_monitor/Dockerfile

@@ -66,8 +66,8 @@ HEALTHCHECK --interval=10s --timeout=1s \
 
 FROM trafficmonitor-dependencies as get-delve
 
-RUN dnf -y install golang git && \
-    go get -u github.com/go-delve/delve/cmd/dlv
+RUN dnf -y install golang && \
+    GOPROXY='https://proxy.golang.org' go get -u github.com/go-delve/delve/cmd/dlv
 
 FROM trafficmonitor as trafficmonitor-debug
 COPY --from=get-delve /root/go/bin /usr/bin

infrastructure/cdn-in-a-box/traffic_ops/Dockerfile

@@ -114,8 +114,8 @@ HEALTHCHECK --interval=10s --timeout=1s \
 
 FROM trafficops-dependencies as get-delve
 
-RUN dnf -y install git golang && \
-    go get -u github.com/go-delve/delve/cmd/dlv
+RUN dnf -y install golang && \
+    GOPROXY='https://proxy.golang.org' go get -u github.com/go-delve/delve/cmd/dlv
 
 FROM trafficops AS trafficops-debug
 COPY --from=get-delve /root/go/bin /usr/bin

infrastructure/cdn-in-a-box/traffic_stats/Dockerfile

@@ -58,8 +58,8 @@ ENTRYPOINT /run.sh
 
 FROM trafficstats-dependencies AS get-delve
 
-RUN dnf -y install golang git && \
-    go get -u github.com/go-delve/delve/cmd/dlv
+RUN dnf -y install golang && \
+    GOPROXY='https://proxy.golang.org' go get -u github.com/go-delve/delve/cmd/dlv
 
 FROM trafficstats AS trafficstats-debug
 COPY --from=get-delve /root/go/bin /usr/bin