[Go Modules] Add proxy

Dockerfile

@@ -10,6 +10,7 @@ RUN mkdir -p /app/prebid-server/
 WORKDIR /app/prebid-server/
 ENV GOROOT=/usr/local/go
 ENV PATH=$GOROOT/bin:$PATH
+ENV GOPROXY="https://proxy.golang.org"
 RUN apt-get update && \
     apt-get install -y git && \
     apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

Makefile

@@ -13,8 +13,8 @@ all:
 # deps will clean out the vendor directory and use go mod for a fresh install
 deps:
 	rm -rf vendor
-	go mod vendor
-	go mod tidy
+	go mod vendor -v
+	go mod tidy -v
 
 # test will ensure that all of our dependencies are available and run validate.sh
 test: deps
@@ -29,8 +29,8 @@ test: deps
 
 # build will ensure all of our tests pass and then build the go binary
 build: test
-	go build -mod=vendor ./...
+	$GOPROXY go build -mod=vendor ./...
 
 # image will build a docker image
 image: build
-	docker build -t prebid-server .
+	docker build -t prebid-server .