Do not put complex logic or long-running tasks in package init() functions. Keep init() minimal (if you use it at all), such as simple registration of types or default variable initialization. Perform real setup in explicit functions (like in main or a setup function called by main).
init() runs before main and in an undefined order across packages, which can lead to unpredictable behavior and make testing harder. Complex init logic can slow down program start and hide dependencies. Keeping initialization explicit improves clarity and control over program startup.
Side-by-side examples engineers can pattern-match during review.
var DefaultClient *Client
func init() {
// Complex or external setup in init
cfg := loadConfigFromDisk() // reading file, etc.
DefaultClient = NewClient(cfg)
}var DefaultClient *Client
func InitClient() error {
cfg, err := loadConfigFromDisk()
if err != nil {
return err
}
DefaultClient = NewClient(cfg)
return nil
}
func main() {
if err := InitClient(); err != nil {
log.Fatal(err)
}
// ... proceed with DefaultClient ready
}From the same buckets as this rule.