go vet & Common Analyzer Diagnostics

go vet inspects Go source for constructs that compile but are probably wrong.

Every team should run go vet ./... locally and in CI, understand the common diagnostics, and know when deeper analyzers add value.

Recipe

Quick-reference recipe card - copy-paste ready.

# All packages in module
go vet ./...
 
# Specific packages
go vet ./internal/...
 
# List available analyzers (Go 1.26+)
go tool vet help
 
# Run vet via test harness (some teams prefer)
go test -vet=off ./...   # disable vet during test when running separately

When to reach for this:

• CI baseline before adding golangci-lint.
• Debugging mysterious printf or JSON tag failures.
• After upgrading Go minor versions (read release notes for new vet checks).
• Teaching juniors why code "compiles but smells wrong."

Working Example

Buggy handler:

package api
 
import (
    "encoding/json"
    "fmt"
    "net/http"
)
 
type User struct {
    Name string `json:name` // invalid tag syntax
}
 
func Handler(w http.ResponseWriter, r *http.Request) {
    u := User{Name: "ada"}
    _ = json.NewEncoder(w).Encode(u)
    fmt.Printf("user %d", u.Name) // format verb mismatch
}

Run:

go vet ./...

Typical output:

api/handler.go:12:2: fmt.Printf format %d has arg u.Name of wrong type string
api/handler.go:8:5: struct field tag `json:name` not compatible with reflect.StructTag.Get: bad syntax for struct tag pair

Fixed code:

type User struct {
    Name string `json:"name"`
}
 
func Handler(w http.ResponseWriter, r *http.Request) {
    u := User{Name: "ada"}
    _ = json.NewEncoder(w).Encode(u)
    fmt.Printf("user %s", u.Name)
}

What this demonstrates:

• Vet catches Printf verb mistakes without running the program.
• structtag analyzer validates JSON tag syntax before marshaling surprises in production.
• Fixes are source changes, not linter suppressions.

Deep Dive

How It Works

• Vet loads packages using the same build context as go test.
• Each analyzer is a function registered with the vet driver (many built on go/analysis).
• Diagnostics include file, line, and a human-readable message.
• Build tags, GOOS, and GOARCH affect which files vet examines.

Common Vet Analyzers (Representative)

Relationship to golangci-lint

golangci-lint's govet linter wraps vet analyzers and may enable additional checks.

Running go vet alone is simpler in scripts; golangci-lint centralizes severity and excludes.

# .golangci.yml excerpt
linters:
  enable:
    - govet
linters-settings:
  govet:
    enable-all: true

Go Notes

// copylocks example - vet flags copying sync.Mutex
type Bad struct {
    mu sync.Mutex
}
 
func use(b Bad) { // vet: passes lock by value
    b.mu.Lock()
}

Prefer pointer receivers or do not embed locks in copied structs.

When Vet Is Not Enough

Gotchas

• Assuming vet is unchanged across Go upgrades - New minors add checks; CI may fail on legacy code. Fix: Read release notes; run go vet on upgrade branch early.
• Running vet only on main packages - Bugs hide in internal/. Fix: Always go vet ./....
• Ignoring copylocks in hot paths - Passing locked structs copies mutex state. Fix: Use pointers or redesign API.
• Suppressing printf warnings - Almost always a real bug. Fix: Correct the verb or use %v deliberately with comment.
• Mismatched build tags between editor and CI - Vet skips files CI does not see. Fix: Align tags in gopls settings and CI GOFLAGS.
• Using //nolint:govet broadly - Hides future real issues. Fix: Narrow suppressions to one line with justification ticket.

Alternatives

FAQs

Related

• Go Code Quality: Opinionated by Design - quality stack overview
• Code Quality Basics - first vet invocation
• golangci-lint Configuration - govet settings
• staticcheck & golangci-lint in CI - deeper analyzers
• CI Quality Gates: Lint, Test, Race, Vuln - vet in pipeline

Stack versions: This page was written for Go 1.26.x (Green Tea GC default, go fix modernizers - verify patch at build), chi (latest - verify at build), gin (latest - verify at build), echo (latest - verify at build), google.golang.org/grpc (latest - verify at build), sigs.k8s.io/controller-runtime (latest - verify at build), kubebuilder (latest - verify at build), tinygo (latest - verify board targets at build), wazero (latest - verify at build), and golangci-lint (latest - verify linter set at build).