// Before (synchronous):
_ = config.SaveEmailBody(folderForCache, config.CachedEmailBody{...})

// After (synchronous):
err := config.SaveEmailBody(folderForCache, config.CachedEmailBody{...})
if err != nil {
    log.Printf("debug: error caching email body fails (disk full, permission denied) for UID: %d: %v", msg.UID, err)
}

// Before (asynchronous):
go config.SaveEmailBody(folderName, config.CachedEmailBody{...})

// After (asynchronous):
go func() {
    err := config.SaveEmailBody(folderName, config.CachedEmailBody{...})
    if err != nil {
        log.Printf("debug: error caching email body fails (disk full, permission denied) for UID: %d: %v", msg.UID, err)
    }
}()