PMM-4010 Update Travis CI config. (#28)

Author: AlekSi

.travis.yml

@@ -1,7 +1,28 @@
-dist: trusty
-sudo: required
+dist: bionic
 language: go
 
+services:
+  - docker
+
+go:
+  - 1.12.x
+  - 1.13.x
+  - master
+
+matrix:
+  fast_finish: true
+  allow_failures:
+    - go: master
+
+cache:
+  directories:
+    - /home/travis/.cache/go-build
+    # - /home/travis/gopath/pkg
+
+before_cache:
+  - go clean -testcache
+  # - go clean -cache
+
 env:
   global:
     # Secure variables are not exposed for external pull requests: https://docs.travis-ci.com/user/pull-requests#Pull-Requests-and-Security-Restrictions
@@ -10,13 +31,5 @@ env:
     # AWS_SECRET_ACCESS_KEY
     - secure: "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"
 
-go:
-  - 1.12.x
-  - 1.11.x
-  - tip
-
-services:
-  - docker
-
 script:
   - make travis

README.md

@@ -1,7 +1,7 @@
 # RDS Exporter
 
 [![Release](https://img.shields.io/github/release/percona/rds_exporter.svg?style=flat)](https://github.com/percona/rds_exporter/releases/latest)
-[![Build Status](https://travis-ci.org/percona/rds_exporter.svg)](https://travis-ci.org/percona/rds_exporter)
+[![Build Status](https://travis-ci.com/percona/rds_exporter.svg?branch=master)](https://travis-ci.com/percona/rds_exporter)
 [![Go Report Card](https://goreportcard.com/badge/github.com/percona/rds_exporter)](https://goreportcard.com/report/github.com/percona/rds_exporter)
 [![CLA assistant](https://cla-assistant.percona.com/readme/badge/percona/rds_exporter)](https://cla-assistant.percona.com/percona/rds_exporter)
 [![codecov.io Code Coverage](https://img.shields.io/codecov/c/github/percona/rds_exporter.svg?maxAge=2592000)](https://codecov.io/github/percona/rds_exporter?branch=master)