chore(travis): bump go version there

Author: georgettica

.travis.yml

@@ -3,12 +3,12 @@ language: go
 sudo: false
 
 go:
-  - 1.13.x
+  - 1.18.x
 
 before_install:
   - go get golang.org/x/tools/cmd/cover
   - go get github.com/mattn/goveralls
 script:
   - make test
 after_success:
-  - bash <(curl -s https://codecov.io/bash)
+  - bash <(curl -s https://codecov.io/bash)