Carry over some changes from #26

Author: mwhooker

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2.1
 
 references:
   images:
-    go: &GOLANG_IMAGE circleci/golang:latest
+    go: &GOLANG_IMAGE circleci/golang:1.13
   environments:
     tmp: &TEST_RESULTS_PATH /tmp/test-results # path to where test results are saved
 

prefix_test.go

@@ -27,6 +27,9 @@ func TestPrefix_NilError(t *testing.T) {
 func TestPrefix_NonError(t *testing.T) {
 	original := errors.New("foo")
 	result := Prefix(original, "bar")
+	if result == nil {
+		t.Fatal("error result was nil")
+	}
 	if result.Error() != "bar foo" {
 		t.Fatalf("bad: %s", result)
 	}