Go "go vet" Failures in CI - Fix Vet Errors That Fail the Build

go vet reports suspicious constructs the compiler accepts but are likely bugs. Because go test runs a subset of vet by default, a vet finding fails the test run before any test executes.

What this error means

A go vet ./... step fails, or go test reports a vet: error and stops. The message names a specific issue - a Printf format mismatch, a copied lock, a malformed struct tag - at an exact file and line.

go vet output

# github.com/yourorg/app
./log.go:22:2: fmt.Printf format %d has arg name of wrong type string
./model.go:9:2: struct field tag `json:name` not compatible with reflect.StructTag.Get

Common causes

Printf/Sprintf format mismatch

A format verb does not match its argument type (%d with a string), or the argument count is wrong. vet catches these even though they compile.

Malformed struct tags

A struct tag with bad syntax (missing quotes, wrong separator) does not parse via reflect.StructTag.Get, so vet flags it.

Copied locks or unreachable code

Passing a struct containing a sync.Mutex by value, or code after a return, are common vet findings.

How to fix it

Fix the construct vet names

Read the file:line - vet points at the exact problem.
Correct the Printf verb/args, fix the struct tag syntax, or pass the locked struct by pointer.
Re-run go vet ./... until clean.

Run vet explicitly and treat it as a gate

Terminal

go vet ./...
go test ./...   # also runs the default vet subset

How to prevent it

Run go vet ./... as a dedicated CI step.
Keep go test vet enabled (do not pass -vet=off).
Add a linter (e.g. go vet plus staticcheck) to catch more issues early.