Update go check to currently supported versions

Author: liggitt

.github/workflows/test.yml

@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-versions: [1.15.x]
+        go-versions: [1.15.x, 1.16.x]
         platform: [ubuntu-latest]
     runs-on: ${{ matrix.platform }}
     steps:

Makefile

@@ -51,9 +51,8 @@ lint:
 check_go_version:
 	@OUTPUT=`go version`; \
 	case "$$OUTPUT" in \
-	*"go1.13"*);; \
-	*"go1.14"*);; \
 	*"go1.15"*);; \
+	*"go1.16"*);; \
 	*"devel"*);; \
 	*) \
 		echo "Expected: go version go1.13.*, go1.14.*, go1.15.*, or devel"; \