Enable goimports linter

Enable `goimports` golangci-lint linter and fix issues.

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

.golangci.yml

@@ -1,17 +1,9 @@
 linters:
   enable:
     - depguard
+    - goimports
     - misspell
     - revive
-  disable:
-    # Disable soon to deprecated[1] linters that lead to false
-    # positives when build tags disable certain files[2]
-    # 1: https://github.com/golangci/golangci-lint/issues/1841
-    # 2: https://github.com/prometheus/node_exporter/issues/1545
-    - deadcode
-    - unused
-    - structcheck
-    - varcheck
 
 issues:
   exclude-rules:

collector/cpufreq_linux.go

@@ -18,10 +18,11 @@ package collector
 
 import (
 	"fmt"
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/procfs/sysfs"
 	"log/slog"
 	"strings"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/procfs/sysfs"
 )
 
 type cpuFreqCollector struct {

collector/interrupts_common.go

@@ -18,9 +18,10 @@
 package collector
 
 import (
+	"log/slog"
+
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/prometheus/client_golang/prometheus"
-	"log/slog"
 )
 
 type interruptsCollector struct {

collector/runit.go

@@ -17,10 +17,11 @@
 package collector
 
 import (
+	"log/slog"
+
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/prometheus-community/go-runit/runit"
 	"github.com/prometheus/client_golang/prometheus"
-	"log/slog"
 )
 
 var runitServiceDir = kingpin.Flag("collector.runit.servicedir", "Path to runit service directory.").Default("/etc/service").String()

collector/selinux_linux.go

@@ -17,9 +17,10 @@
 package collector
 
 import (
+	"log/slog"
+
 	"github.com/opencontainers/selinux/go-selinux"
 	"github.com/prometheus/client_golang/prometheus"
-	"log/slog"
 )
 
 type selinuxCollector struct {

collector/softirqs_common.go

@@ -18,9 +18,10 @@ package collector
 
 import (
 	"fmt"
+	"log/slog"
+
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/procfs"
-	"log/slog"
 )
 
 type softirqsCollector struct {

collector/uname.go

@@ -18,8 +18,9 @@
 package collector
 
 import (
-	"github.com/prometheus/client_golang/prometheus"
 	"log/slog"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 var unameDesc = prometheus.NewDesc(