update dockerfile

Dockerfile

 # NOTE: USING THIS IMAGE UNTIL registry1 credentials are added to IL2 runners
 # Build the manager binary
-FROM registry.il2.dso.mil/platform-one/devops/pipeline-templates/valkyrie/golang-builder-1.6:1.0 as builder
-
+FROM registry.il2.dso.mil/platform-one/devops/pipeline-templates/valkyrie/golang-builder-1.16:1.0 as builder
+USER root
 WORKDIR /workspace
 # set go module cache
 ENV GOMODCACHE=/workspace/.gomodcache
 # Copy the Go Modules manifests
 COPY . .
-USER root
-RUN chmod 755 go.sum
+# RUN chmod 755 go.sum
 # download with json logging
 # RUN go mod download -json
 RUN go mod download

README.md

@@ -3,7 +3,15 @@
 ## Env Variables
 - for local building and to closer simulate the pipeline set
   - from root folder of project
+  - Note: GOMODCACHE seems to be only supported in go 1.16 +
   - export GOMODCACHE=$(pwd)/.gomodcache
+  - example:
+```
+export GOMODCACHE=.gomodcache
+go mod download -json
+find .gomodcache | wc -l
+docker build --progress plain -t abr .
+```
 
 ### Golang Frameworks
 - kubebuilder