Support Go execd plugins with shim (#7283)

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

@@ -0,0 +1,60 @@
+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)
+	}
+}

plugins/inputs/execd/shim/example/cmd/plugin.conf

@@ -0,0 +1,2 @@
+[[inputs.my_plugin_name]]
+	value_name = "value"