Fix example usage

README.md

@@ -7,11 +7,9 @@ registry.
 
 ```yaml
 delete-tag:
-  image: rg.fr-par.scw.cloud/hamburghammer/scaleway-delete-image-plugin/plugin
+  image: rg.fr-par.scw.cloud/hamburghammer/scaleway-delete-image-plugin
   secrets: [token]
   settings:
-    token:
-      from_secret: scaleway_token
     image-name: foo/bar
     tag: latest
     region: fr-par

main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -54,6 +55,14 @@ func (p *Plugin) Flags() []cli.Flag {
 }
 
 func (p *Plugin) Execute(ctx context.Context) error {
+	missingFlags := requiredFlags(p.Settings)
+	if len(missingFlags) != 0 {
+		log.Error().Msg("following flags are missing:")
+		for _, errMsg := range missingFlags {
+			log.Error().Msg("-" + errMsg)
+		}
+		return errors.New("missing required flags")
+	}
 	log.Info().Msg("start")
 	token := p.Settings.Token
 	region := p.Settings.Region
@@ -78,6 +87,23 @@ func (p *Plugin) Execute(ctx context.Context) error {
 	return nil
 }
 
+func requiredFlags(settings *Settings) []string {
+	var errorList []string
+	if settings.ImageName == "" {
+		errorList = append(errorList, "image-name")
+	}
+	if settings.Tag == "" {
+		errorList = append(errorList, "tag")
+	}
+	if settings.Region == "" {
+		errorList = append(errorList, "region")
+	}
+	if settings.Token == "" {
+		errorList = append(errorList, "token")
+	}
+	return errorList
+}
+
 func main() {
 	p := &Plugin{
 		Settings: &Settings{},