check if flags are set

go.mod

@@ -2,4 +2,4 @@ module github.com/containeroo/dologen
 
 go 1.16
 
-require github.com/spf13/pflag v1.0.5 // indirect
+require github.com/spf13/pflag v1.0.5

main.go

@@ -4,15 +4,32 @@ import (
 	"encoding/base64"
 	"fmt"
 	flag "github.com/spf13/pflag"
+	"os"
 )
 
 func main() {
 	username := flag.StringP("username", "u", "", "username for docker registry")
 	password := flag.StringP("password", "p", "", "password for docker registry")
 	server := flag.StringP("server", "s", "", "docker registry server")
-	base64Output := flag.BoolP("base64", "b", false, "output result in base64 encoding")
+	base64Output := flag.BoolP("base64", "b", false, "output result base64 encoded")
 	flag.Parse()
 
+	if *username == "" {
+		fmt.Println("username cannot be empty!")
+		flag.Usage()
+		os.Exit(1)
+	}
+	if *password == "" {
+		fmt.Println("password cannot be empty!")
+		flag.Usage()
+		os.Exit(1)
+	}
+	if *server == "" {
+		fmt.Println("server cannot be empty!")
+		flag.Usage()
+		os.Exit(1)
+	}
+
 	auth := base64.StdEncoding.EncodeToString([]byte(fmt.Sprintf("%s:%s", *username, *password)))
 
 	result := fmt.Sprintf("{\"auths\":{\"%s\":{\"username\":\"%s\",\"password\":\"%s\",\"auth\":\"%s\"}}}", *server, *username, *password, auth)