Now it works - except it doesn't. Maybe I shouldn't hide the error in the compactor.

build/.env.template

@@ -16,4 +16,3 @@ BACKUP_S3_ACCESS_ID=0000000000000000000000000
 BACKUP_S3_SECRET_ID=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
 BACKUP_S3_ENDPOINT=https://s3.us-east-005.backblazeb2.com
 BACKUP_S3_REGION=us-east-005
-BACKUP_SOURCE_PATH=/backups/guestbooky_$(date +\%Y-\%m-\%d)

build/docker-compose.public.yml

@@ -66,7 +66,7 @@ services:
       --username ${GUESTBOOKY_USER}
       --password ${GUESTBOOKY_USER}
       --authenticationDatabase ${GUESTBOOKY_DB_NAME}
-      --out ${BACKUP_SOURCE_PATH} && touch /backups/backup_done"
+      --out /backups/guestbooky_$(date +\%Y-\%m-\%d) && touch /backups/backup_done"
     volumes:
       - ./backups:/backups
     depends_on:
@@ -88,10 +88,9 @@ services:
       BACKUP_S3_SECRET_ID: ${BACKUP_S3_SECRET_ID}
       BACKUP_S3_ENDPOINT: ${BACKUP_S3_ENDPOINT}
       BACKUP_S3_REGION: ${BACKUP_S3_REGION}
-      BACKUP_SOURCE_PATH: ${BACKUP_SOURCE_PATH}
-      BACKUP_DESTINATION_PATH: ${BACKUP_SOURCE_PATH}.gzip
     volumes:
       - ./backups:/backups
+    command: sh -c "export BACKUP_SOURCE_PATH=/backups/guestbooky_$(date +\%Y-\%m-\%d) && export BACKUP_DESTINATION_PATH=/backups/guestbooky_$(date +\%Y-\%m-\%d).gzip && /root/guestbooky-backup"
 
 volumes:
   mongodata:

src/Guestbooky-backup/internal/compactor/compactor.go

@@ -34,7 +34,7 @@ func Compact(source, destination string) error {
 	defer zipWriter.Close()
 
 	if _, err := io.Copy(zipWriter, originFileHandle); err != nil {
-		return errors.New("failed to copy file")
+		return errors.New("failed to copy zip to destination file: " + err.Error()) //nolint:wraperr
 	}
 
 	return nil