test: fixes failing test in go1.10

pkg/plugins/datasource/wrapper/datasource_plugin_wrapper_test.go

@@ -75,7 +75,7 @@ func TestMappingRowValue(t *testing.T) {
 	boolRowValue, _ := dpw.mapRowValue(&datasource.RowValue{Kind: datasource.RowValue_TYPE_BOOL, BoolValue: true})
 	haveBool, ok := boolRowValue.(bool)
 	if !ok || haveBool != true {
-		t.Fatalf("Expected true, was %s", haveBool)
+		t.Fatalf("Expected true, was %v", haveBool)
 	}
 
 	intRowValue, _ := dpw.mapRowValue(&datasource.RowValue{Kind: datasource.RowValue_TYPE_INT64, Int64Value: 42})