Static Analysis with go vet

In this lesson, explore static analysis with go vet through one small Go program, and connect its output to the language rules behind it.

go vet examines code for patterns likely to be mistakes, such as suspicious formatting arguments and misuse of some APIs. Run go vet ./... over a module.

Vet is not a compiler, unit test or complete proof of correctness. Combine it with the race detector, tests and review.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

Command: go vet ./.... Official reference: cmd/vet.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import "fmt"

func main() {
	name := "Go"
	version := 1
	fmt.Printf("%s lesson %d\n", name, version)
}

Output

Go lesson 1

Printf receives a string for %s and an integer for %d. This is valid code that should pass vet’s format checks.

• Format strings and argument types should match.
• A clean vet run does not guarantee absence of all bugs.

Try a deliberately mismatched fmt.Printf argument in a scratch file and see how go vet reports it.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Static Analysis with go vet in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.