update: submit test result to codecov

Author: changkun

.travis.yml

@@ -1,7 +1,10 @@
 language: go
 
-script:
+before_install:
   - make tests
 
+script:
+  - go test -v -race -timeout 60m -coverprofile=coverage.txt -covermode=atomic ./...
+
 after_success:
   - bash <(curl -s https://codecov.io/bash)