bump go version to 1.16 & bump client go to 0.22 & fix panic

.github/workflows/workflow.yml

@@ -11,9 +11,9 @@ on:
 jobs:
   go_unit_tests:
     name: Go unit tests
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     container:
-      image: golang:1.12.9
+      image: golang:1.16
     steps:
     - name: Checkout code
       uses: actions/checkout@v1

go.mod

@@ -1,15 +1,15 @@
 module github.com/wercker/stern
 
-go 1.12
+go 1.16
 
 require (
 	github.com/fatih/color v0.0.0-20180516100307-2d684516a886
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
 	github.com/mattn/go-colorable v0.1.7 // indirect
 	github.com/mitchellh/go-homedir v0.0.0-20161203194507-b8bc1bf76747
-	github.com/pkg/errors v0.0.0-20180311214515-816c9085562c
+	github.com/pkg/errors v0.9.1
 	github.com/spf13/cobra v0.0.0-20180629152535-a114f312e075
-	k8s.io/api v0.18.6
-	k8s.io/apimachinery v0.18.6
-	k8s.io/client-go v0.18.6
+	k8s.io/api v0.22.1
+	k8s.io/apimachinery v0.22.1
+	k8s.io/client-go v0.22.1
 )