Bring Go current in Travis

Signed-off-by: Gábor Lipták <gliptak@gmail.com>

.travis.yml

@@ -1,7 +1,7 @@
 language: go
 
 go:
-  - 1.10.x
+  - 1.11.x
 
 sudo: required
 

hack/build-image/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang:1.10-alpine3.8
+FROM golang:1.11-alpine3.8
 
 RUN apk add --update --no-cache git bash && \
     mkdir -p /go/src/k8s.io && \