add test coverage

.travis.yml

@@ -1,9 +1,15 @@
 language: go
 go:
-  - "1.11"
-  - "1.12"
+  # The stretchr/testify test framework no longer supports go v1.11 and v1.12 since July 20, 2020.
+  # - "1.11"
+  # - "1.12" 
   - "1.13"
+  - "1.14"
 before_install:
   - go get github.com/xeipuuv/gojsonreference
   - go get github.com/xeipuuv/gojsonpointer
   - go get github.com/stretchr/testify/assert
+script:
+  - go test -coverpkg=./... -coverprofile=coverage.info -timeout=5s
+after_succese:
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,6 +1,7 @@
 [![GoDoc](https://godoc.org/github.com/xeipuuv/gojsonschema?status.svg)](https://godoc.org/github.com/xeipuuv/gojsonschema)
 [![Build Status](https://travis-ci.org/xeipuuv/gojsonschema.svg)](https://travis-ci.org/xeipuuv/gojsonschema)
 [![Go Report Card](https://goreportcard.com/badge/github.com/xeipuuv/gojsonschema)](https://goreportcard.com/report/github.com/xeipuuv/gojsonschema)
+[![Coverage](https://codecov.io/gh/xeipuuv/gojsonschema/branch/master/graph/badge.svg)](https://codecov.io/gh/xeipuuv/gojsonschema)
 
 # gojsonschema