Exit Once
If possible, prefer to call os.Exit or log.Fatal at most once in your
main(). If there are multiple error scenarios that halt program execution,
put that logic under a separate function and return errors from it.
This has the effect of shortening your main() function and putting all key
business logic into a separate, testable function.
| Bad | Good |
|---|---|
| ```go package main func main() { args := os.Args[1:] if len(args) != 1 { log.Fatal("missing file") } name := args[0] f, err := os.Open(name) if err != nil { log.Fatal(err) } defer f.Close() // If we call log.Fatal after this line, // f.Close will not be called. b, err := io.ReadAll(f) if err != nil { log.Fatal(err) } // ... } ``` | ```go package main func main() { if err := run(); err != nil { log.Fatal(err) } } func run() error { args := os.Args[1:] if len(args) != 1 { return errors.New("missing file") } name := args[0] f, err := os.Open(name) if err != nil { return err } defer f.Close() b, err := io.ReadAll(f) if err != nil { return err } // ... } ``` |