Drop support for Go 1.9 (#6026)

.circleci/config.yml

@@ -2,9 +2,6 @@
 defaults:
   defaults: &defaults
     working_directory: '/go/src/github.com/influxdata/telegraf'
-  go-1_9: &go-1_9
-    docker:
-      - image: 'quay.io/influxdb/telegraf-ci:1.9.7'
   go-1_10: &go-1_10
     docker:
       - image: 'quay.io/influxdb/telegraf-ci:1.10.8'
@@ -35,14 +32,6 @@ jobs:
           paths:
             - '*'
 
-  test-go-1.9:
-    <<: [ *defaults, *go-1_9 ]
-    steps:
-      - attach_workspace:
-          at: '/go/src'
-      # disabled due to gofmt differences (1.10 vs 1.11).
-      #- run: 'make check'
-      - run: 'make test'
   test-go-1.10:
     <<: [ *defaults, *go-1_10 ]
     steps:
@@ -109,12 +98,6 @@ workflows:
           filters:
             tags:
               only: /.*/
-      - 'test-go-1.9':
-          requires:
-            - 'deps'
-          filters:
-            tags:
-              only: /.*/
       - 'test-go-1.10':
           requires:
             - 'deps'
@@ -141,14 +124,12 @@ workflows:
               only: /.*/
       - 'package':
           requires:
-            - 'test-go-1.9'
             - 'test-go-1.10'
             - 'test-go-1.11'
             - 'test-go-1.12'
             - 'test-go-1.12-386'
       - 'release':
           requires:
-            - 'test-go-1.9'
             - 'test-go-1.10'
             - 'test-go-1.11'
             - 'test-go-1.12'
@@ -161,9 +142,6 @@ workflows:
   nightly:
     jobs:
       - 'deps'
-      - 'test-go-1.9':
-          requires:
-            - 'deps'
       - 'test-go-1.10':
           requires:
             - 'deps'
@@ -178,7 +156,6 @@ workflows:
             - 'deps'
       - 'nightly':
           requires:
-            - 'test-go-1.9'
             - 'test-go-1.10'
             - 'test-go-1.11'
             - 'test-go-1.12'

README.md

@@ -40,9 +40,9 @@ Ansible role: https://github.com/rossmcdonald/telegraf
 
 ### From Source:
 
-Telegraf requires golang version 1.9 or newer, the Makefile requires GNU make.
+Telegraf requires golang version 1.10 or newer, the Makefile requires GNU make.
 
-1. [Install Go](https://golang.org/doc/install) >=1.9 (1.11 recommended)
+1. [Install Go](https://golang.org/doc/install) >=1.10 (1.12 recommended)
 2. [Install dep](https://golang.github.io/dep/docs/installation.html) ==v0.5.0
 3. Download Telegraf source:
    ```