Bump Go version to 1.13.x

Signed-off-by: Yuri Shkuro <ys@uber.com>

.travis.yml

@@ -7,43 +7,43 @@ dist: trusty
 
 jobs:
   include:
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - TESTS=true
     - COVERAGE=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - PROTO_GEN_TEST=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - ALL_IN_ONE=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - CROSSDOCK=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - DOCKER=true
     - DEPLOY=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - ES_INTEGRATION_TEST=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - KAFKA_INTEGRATION_TEST=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - CASSANDRA_INTEGRATION_TEST=true
-  - go: "1.12.1"
+  - go: "1.13.x"
     env:
     - HOTROD=true
   - stage: Fuzz regression
     dist: bionic
-    go: 1.12.x
+    go: "1.13.x"
     script: ./scripts/travis/fuzzit.sh local-regression
   - stage: Fuzz
     if: branch = master AND type IN (push)
     dist: bionic
-    go: 1.12.x
+    go: "1.13.x"
     script: ./scripts/travis/fuzzit.sh fuzzing
 
 services: