Update Go to 1.21 (#190)

* Update Go build to 1.21.
* Update minimum Go version to 1.20.
* Remove obsolete build flags.

Signed-off-by: SuperQ <superq@gmail.com>

.circleci/config.yml

@@ -6,10 +6,10 @@ executors:
   # Whenever the Go version is updated here, .promu.yml should also be updated.
   golang:
     docker:
-      - image: cimg/go:1.20
+      - image: cimg/go:1.21
   golang_memcached:
     docker:
-      - image: cimg/go:1.20
+      - image: cimg/go:1.21
       - image: memcached
 jobs:
   test:

.github/workflows/golangci-lint.yml

@@ -22,7 +22,7 @@ jobs:
       - name: install Go
         uses: actions/setup-go@6edd4406fa81c3da01a34fa6f6343087c207a568 # v3.5.0
         with:
-          go-version: 1.20.x
+          go-version: 1.21.x
       - name: Install snmp_exporter/generator dependencies
         run: sudo apt-get update && sudo apt-get -y install libsnmp-dev
         if: github.repository == 'prometheus/snmp_exporter'

.promu.yml

@@ -1,14 +1,13 @@
 go:
     # Whenever the Go version is updated here, .circle/config.yml should also
     # be updated.
-    version: 1.20
+    version: 1.21
 repository:
     path: github.com/prometheus/memcached_exporter
 build:
     binaries:
         - name: memcached_exporter
           path: ./cmd/memcached_exporter
-    flags: -a -tags netgo
     ldflags: |
         -X github.com/prometheus/common/version.Version={{.Version}}
         -X github.com/prometheus/common/version.Revision={{.Revision}}

go.mod

@@ -1,6 +1,6 @@
 module github.com/prometheus/memcached_exporter
 
-go 1.18
+go 1.20
 
 require (
 	github.com/alecthomas/kingpin/v2 v2.4.0