upgrade to go 1.16 (#118)

Dockerfile

@@ -1,13 +1,18 @@
 # Build the manager binary
-FROM gcr.io/gcp-runtimes/go1-builder:1.15 as builder
+FROM registry.access.redhat.com/ubi8/ubi:latest as builder
+
+RUN INSTALL_PKGS="go-toolset git" && \
+    yum install -y --setopt=tsflags=nodocs $INSTALL_PKGS && \
+    rpm -V $INSTALL_PKGS && \
+    yum clean all -y
 
 WORKDIR /workspace
 # Copy the Go Modules manifests
 COPY go.mod go.mod
 COPY go.sum go.sum
 # cache deps before building and copying source so that we do not need to re-download as much
 # and so that source changes do not invalidate our downloaded layer
-RUN /usr/local/go/bin/go mod download
+RUN go mod download
 
 # Copy the go source
 COPY main.go main.go
@@ -28,7 +33,7 @@ COPY .git .git
 RUN GIT_COMMIT=$(git rev-list -1 HEAD) && \
 echo " injecting GIT COMMIT: $GIT_COMMIT" && \
 CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GO111MODULE=on \
-/usr/local/go/bin/go build -ldflags "-X github.com/project-koku/koku-metrics-operator/controllers.GitCommit=$GIT_COMMIT" -a -o manager main.go
+go build -ldflags "-w -s -X github.com/project-koku/koku-metrics-operator/controllers.GitCommit=$GIT_COMMIT" -a -o manager main.go
 
 # Use distroless as minimal base image to package the manager binary
 # Refer to https://github.com/GoogleContainerTools/distroless for more details