Update tools

This change updates to the following:
* Ubuntu 20.04
* Go 1.16.7
* Minikube 1.22.0 (running Kubernetes 1.15.12)
* Skaffold 1.31.0
* Kubectl 1.15.12

In addition, it adds more documentation to the Kubernetes update script.

.travis.yml

@@ -1,23 +1,28 @@
-dist: xenial
+dist: focal
 
 language: go
 go:
-- "1.13.3"
+- "1.16.7"
 go_import_path: github.com/nats-io/nats-operator
 
 env:
 - KUBERNETES_CONFIG_FILE=$HOME/.kube/config CHANGE_MINIKUBE_NONE_USER=true CLUSTER_SCOPED_E2E_NAMESPACE=nats-io NAMESPACE_SCOPED_E2E_NAMESPACE=nats-operator-e2e
 
+before_install:
+- sudo apt-get update -y
+- sudo apt-get install -y conntrack
+
 install:
 - GO111MODULE=off go get -u github.com/cloudflare/cfssl/cmd/cfssl
 - GO111MODULE=off go get -u github.com/cloudflare/cfssl/cmd/cfssljson
 
 before_script:
 - go version
-- curl -Lo kubectl https://storage.googleapis.com/kubernetes-release/release/v1.12.4/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/
-- curl -Lo minikube https://storage.googleapis.com/minikube/releases/v0.32.0/minikube-linux-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/
-- curl -Lo skaffold https://storage.googleapis.com/skaffold/releases/v0.20.0/skaffold-linux-amd64 && chmod +x skaffold && sudo mv skaffold /usr/local/bin/
-- sudo minikube start --vm-driver=none --kubernetes-version=v1.12.4 --extra-config=apiserver.service-account-signing-key-file=/var/lib/minikube/certs/apiserver.key --extra-config=apiserver.service-account-issuer=api --extra-config=apiserver.service-account-api-audiences=api
+- docker version
+- curl -Lo kubectl https://storage.googleapis.com/kubernetes-release/release/v1.15.12/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/
+- curl -Lo minikube https://storage.googleapis.com/minikube/releases/v1.22.0/minikube-linux-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/
+- curl -Lo skaffold https://storage.googleapis.com/skaffold/releases/v1.31.0/skaffold-linux-amd64 && chmod +x skaffold && sudo mv skaffold /usr/local/bin/
+- minikube start --vm-driver=docker --kubernetes-version=v1.15.12 --extra-config=apiserver.service-account-signing-key-file=/var/lib/minikube/certs/apiserver.key --extra-config=apiserver.service-account-issuer=api --extra-config=apiserver.service-account-api-audiences=api
 - minikube update-context
 - JSONPATH='{range .items[*]}{@.metadata.name}:{range @.status.conditions[*]}{@.type}={@.status};{end}{end}'; until kubectl get nodes -o jsonpath="$JSONPATH" 2>&1 | grep -q "Ready=True"; do sleep 1; done
 

go.mod

@@ -1,6 +1,6 @@
 module github.com/nats-io/nats-operator
 
-go 1.13
+go 1.16
 
 require (
  cloud.google.com/go v0.47.0 // indirect

hack/update-kube-version.sh

@@ -1,21 +1,47 @@
 #!/bin/sh
 set -euo pipefail
 
+# Usage
+# In order to update k8s.io/kubernetes, we also have to update modules at
+# k8s.io/XXX.
+#
+# To update the Kubernetes dependencies, first look for a tag here:
+# https://github.com/kubernetes/kubernetes/releases
+#
+# Then, run this command:
+# ./update-kube-version.sh 1.22.1
+#
+# This will update the go.mod file with the required sub-dependency versions
+# and only then update the kubernetes version.
+
 VERSION=${1#"v"}
 if [ -z "$VERSION" ]; then
  echo "Must specify version!"
  exit 1
 fi
+echo "Specified version ${VERSION}"
+
+echo "Checking which modules need updating..."
 MODS=($(
  curl -sS https://raw.githubusercontent.com/kubernetes/kubernetes/v${VERSION}/go.mod |
  sed -n 's|.*k8s.io/\(.*\) => ./staging/src/k8s.io/.*|k8s.io/\1|p'
 ))
+echo "Found ${#MODS[@]} modules"
+
+i=0
 for MOD in "${MODS[@]}"; do
  V=$(
  go mod download -json "${MOD}@kubernetes-${VERSION}" |
  sed -n 's|.*"Version": "\(.*\)".*|\1|p'
  )
  go mod edit "-replace=${MOD}=${MOD}@${V}"
+
+ i=$[i + 1]
+ echo "Updated ${MOD} (${i}/${#MODS[@]})"
 done
+
+echo "Lastly, updating k8s.io/kubernetes..."
 go get "k8s.io/kubernetes@v${VERSION}"
+go mod tidy
 
+echo "Done!"