Adds -race and go 1.12

.travis.yml

@@ -6,9 +6,10 @@ services:
 
 go:
   - 1.11.x
+  - 1.12.x
 
 matrix:
   fast_finish: true
 
 script:
-  - go test -v -run=.
+  - go test -v -race -run=.