feat: lets support multiple go version again....

.travis.yml

 language: go
 
 go:
+  - 1.12.x
   - 1.13.x
+  - tip
+
+os:
+  - linux
+  - osx
+  - windows
 
 env:
   global:
@@ -32,10 +39,5 @@ before_install:
 script:
   - go test -v  $(go list ./... | grep -v /languages/)  -race -coverprofile=coverage.txt -covermode=atomic
 
-os:
-  - linux
-  - osx
-  - windows
-
 after_success:
   - bash <(curl -s https://codecov.io/bash)