Move usage string to internal to fix `go run`

cmd/telegraf/telegraf.go

@@ -13,6 +13,7 @@ import (
 	"syscall"
 
 	"github.com/influxdata/telegraf/agent"
+	"github.com/influxdata/telegraf/internal"
 	"github.com/influxdata/telegraf/internal/config"
 	"github.com/influxdata/telegraf/logger"
 	_ "github.com/influxdata/telegraf/plugins/aggregators/all"
@@ -192,7 +193,7 @@ func reloadLoop(
 }
 
 func usageExit(rc int) {
-	fmt.Println(usage)
+	fmt.Println(internal.Usage)
 	os.Exit(rc)
 }
 

cmd/telegraf/usage.go → internal/usage.go

 // +build !windows
 
-package main
+package internal
 
-const usage = `Telegraf, The plugin-driven server agent for collecting and reporting metrics.
+const Usage = `Telegraf, The plugin-driven server agent for collecting and reporting metrics.
 
 Usage:
 

cmd/telegraf/usage_windows.go → internal/usage_windows.go

 // +build windows
 
-package main
+package internal
 
-const usage = `Telegraf, The plugin-driven server agent for collecting and reporting metrics.
+const Usage = `Telegraf, The plugin-driven server agent for collecting and reporting metrics.
 
 Usage: