Error Handling

Error handling in Go modules follows typical Go error patterns with explicit error return values and if err != nil checks. You can also use error handling to verify user input.

Here is an example module with a function divide(), that throws an error if the denominator is zero:

// A Dagger module for saying hello world!

package main

import (
	"fmt"
)

type MyModule struct {
}

func (*MyModule) Divide(a, b int) (int, error) {
	if b == 0 {
		return 0, fmt.Errorf("cannot divide by zero")
	}
	return a / b, nil
}

Here is an example call for this module:

dagger call divide --a=4 --b=2

The result will be:

2

Here is another example call for this module, this time dividing by zero:

dagger call divide --a=4 --b=0

The result will be:

cannot divide by zero