Upgrade to use golang 1.16

This commit sets the minimal golang version for the project to 1.16.

Dockerfile

@@ -1,4 +1,4 @@
-FROM registry.svc.ci.openshift.org/openshift/release:golang-1.15 AS builder
+FROM registry.svc.ci.openshift.org/openshift/release:golang-1.16 AS builder
 WORKDIR /go/src/sigs.k8s.io/cluster-api-provider-aws
 COPY . .
 # VERSION env gets set in the openshift/release image and refers to the golang version, which interfers with our own

Makefile

@@ -60,7 +60,7 @@ ifeq ($(NO_DOCKER), 1)
   DOCKER_CMD =
   IMAGE_BUILD_CMD = imagebuilder
 else
-  DOCKER_CMD = $(ENGINE) run --rm -e CGO_ENABLED=$(CGO_ENABLED) -e GOARCH=$(GOARCH) -e GOOS=$(GOOS) -v "$(PWD)":/go/src/sigs.k8s.io/cluster-api-provider-aws:Z -w /go/src/sigs.k8s.io/cluster-api-provider-aws openshift/origin-release:golang-1.15
+  DOCKER_CMD = $(ENGINE) run --rm -e CGO_ENABLED=$(CGO_ENABLED) -e GOARCH=$(GOARCH) -e GOOS=$(GOOS) -v "$(PWD)":/go/src/sigs.k8s.io/cluster-api-provider-aws:Z -w /go/src/sigs.k8s.io/cluster-api-provider-aws openshift/origin-release:golang-1.16
   IMAGE_BUILD_CMD = $(ENGINE) build
 endif
 

go.mod

@@ -1,6 +1,6 @@
 module sigs.k8s.io/cluster-api-provider-aws
 
-go 1.15
+go 1.16
 
 require (
 	github.com/aws/aws-sdk-go v1.38.23