Remove go-tip to do not use unnecessary Travis slots

.travis.yml

@@ -9,8 +9,6 @@ addons:
 
 matrix:
   fast_finish: true
-  allow_failures:
-    - go: tip
 
 sudo: required
 
@@ -33,13 +31,12 @@ jobs:
   include:
     - go: 1.10.x
     - go: 1.11.x
-    - go: tip
 
     # Integration test builds for 3rd party clients
     - go: 1.11.x
       script:
         - make TEST=go integration
-    
+
     - language: python
       python: '3.6'
       before_install:
@@ -48,7 +45,7 @@ jobs:
         - go get ./...
       script:
         - make TEST=python-pymysql integration
-    
+
     - language: python
       python: '3.6'
       before_install:
@@ -57,7 +54,7 @@ jobs:
         - go get ./...
       script:
         - make TEST=python-mysql integration
-    
+
     - language: php
       php: '7.1'
       before_install:
@@ -66,7 +63,7 @@ jobs:
         - go get ./...
       script:
         - make TEST=php integration
-    
+
     - language: ruby
       ruby: '2.3'
       before_install:
@@ -75,7 +72,7 @@ jobs:
         - go get ./...
       script:
         - make TEST=ruby integration
-    
+
     - language: java
       jdk: oraclejdk10
       before_install:
@@ -84,7 +81,7 @@ jobs:
         - go get ./...
       script:
         - make TEST=jdbc-mariadb integration
-    
+
     - language: node_js
       node_js: '7'
       before_install:
@@ -93,7 +90,7 @@ jobs:
         - go get ./...
       script:
         - make TEST=javascript integration
-    
+
     - language: csharp
       mono: none
       dotnet: '2.1'