update shim docs to point users in the right direction

plugins/inputs/execd/shim/example/cmd/main.go

@@ -1,60 +1,3 @@
 package main
 
-import (
-	"flag"
-	"fmt"
-	"os"
-	"time"
-
-	// TODO: import your plugins
-	// _ "github.com/my_github_user/my_plugin_repo/plugins/inputs/mypluginname"
-
-	"github.com/influxdata/telegraf/plugins/inputs/execd/shim"
-)
-
-var pollInterval = flag.Duration("poll_interval", 1*time.Second, "how often to send metrics")
-var pollIntervalDisabled = flag.Bool("poll_interval_disabled", false, "how often to send metrics")
-var configFile = flag.String("config", "", "path to the config file for this plugin")
-var err error
-
-// This is designed to be simple; Just change the import above and you're good.
-//
-// However, if you want to do all your config in code, you can like so:
-//
-// // initialize your plugin with any settngs you want
-// myInput := &mypluginname.MyPlugin{
-// 	DefaultSettingHere: 3,
-// }
-//
-// shim := shim.New()
-//
-// shim.AddInput(myInput)
-//
-// // now the shim.Run() call as below.
-//
-func main() {
-	// parse command line options
-	flag.Parse()
-	if *pollIntervalDisabled {
-		*pollInterval = shim.PollIntervalDisabled
-	}
-
-	// create the shim. This is what will run your plugins.
-	shim := shim.New()
-
-	// If no config is specified, all imported plugins are loaded.
-	// otherwise follow what the config asks for.
-	// Check for settings from a config toml file,
-	// (or just use whatever plugins were imported above)
-	err = shim.LoadConfig(configFile)
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Err loading input: %s\n", err)
-		os.Exit(1)
-	}
-
-	// run the input plugin(s) until stdin closes or we receive a termination signal
-	if err := shim.Run(*pollInterval); err != nil {
-		fmt.Fprintf(os.Stderr, "Err: %s\n", err)
-		os.Exit(1)
-	}
-}
+// see /plugins/common/shim/example/cmd/main.go instead.

plugins/inputs/execd/shim/goshim.go

@@ -1,5 +1,7 @@
 package shim
 
+// this package is deprecated. use plugins/common/shim instead
+
 import (
 	"bufio"
 	"context"