Use mattermost v5 module (#1192)

vendor/go.uber.org/multierr/.travis.yml

@@ -5,11 +5,12 @@ go_import_path: go.uber.org/multierr
 env:
   global:
     - GO15VENDOREXPERIMENT=1
+    - GO111MODULE=on
 
 go:
-  - 1.7
-  - 1.8
-  - tip
+  - 1.11.x
+  - 1.12.x
+  - 1.13.x
 
 cache:
   directories:
@@ -18,16 +19,11 @@ cache:
 before_install:
 - go version
 
-install:
-- |
-  set -e
-  make install_ci
-
 script:
 - |
   set -e
   make lint
-  make test_ci
+  make cover
 
 after_success:
 - bash <(curl -s https://codecov.io/bash)