De-duplicate addresses before returning email subscribers

main.go

@@ -115,15 +115,21 @@ func retrieveSubscribers(cfg *Config) ([]string, error) {
 		return nil, errors.New("response format error: 'emails' field not found")
 	}
 
-	/* Convert emails to []string */
+    /* De-duplicate emails using a map */
 	/* *** */
-	var subscribers []string
+	emailMap := make(map[string]bool)
 	for _, email := range emails {
 		if emailStr, ok := email.(string); ok {
-			subscribers = append(subscribers, emailStr)
+			emailMap[emailStr] = true
 		}
 	}
 
+	/* Convert the map keys back to a slice */
+	var subscribers []string
+	for email := range emailMap {
+		subscribers = append(subscribers, email)
+	}
+
 	return subscribers, nil
 }