Table of Contents

• What is a “must” pattern ?
  • How error handling in Go looks like
  • What “must” pattern looks like

What is a “must” pattern ?

It’s about creating helper functions that wrap operations, panicking if an error occurs. It’s often used in scenarios where you know the code is guaranteed to succeed.

How error handling in Go looks like

package main

import (
	"log"
	"os"
	"text/template"
)

func main() {
	tmpl, err := template.New("example").Parse("Hello, {{.}}!")
	if err != nil {
		log.Fatalf("Failed to parse template: %v", err)
	}

	err = tmpl.Execute(os.Stdout, "World")
	if err != nil {
		log.Fatalf("Faided to execute template: %v", err)
	}
}

What “must” pattern looks like

package main

import (
	"log"
	"os"
	"text/template"
)

func main() {
	tmpl := template.Must(template.New("example").Parse("Hello, {{.}}!"))
	tmpl.Execute(os.Stdout, "World")
}

What “must” implementation looks like in this example

func Must(t *Template, err error) *Template {
	if err != nil {
		panic(err)
	}
	return t
}

Generic implementation

func Must[T any](val T, err error) T {
	if err != nil {
		panic(err)
	}
	return val
}