Update go version to 1.12 in check script and travis config

.travis.yml

@@ -6,7 +6,7 @@ services:
 language: go
 
 go:
-  - 1.11.2
+  - 1.12.1
 
 before_install:
   - sudo apt-get install libseccomp-dev -qq

hack/check-go-version.sh

@@ -18,7 +18,7 @@ set -euo pipefail
 
 GO_VERSION=($(go version))
 
-if ! echo "${GO_VERSION[2]}" | grep -Eq 'go1.9|1.10|1.11'; then
+if ! echo "${GO_VERSION[2]}" | grep -Eq '1.12'; then
   echo "Unsupported go version ${GO_VERSION}"
   return 1
 fi