go:embed requires go1.16 or later (-lang was set to %s; chec

Error message

go:embed requires go1.16 or later (-lang was set to %s; check go.mod)

What it means

The //go:embed directive was introduced in Go 1.16. The compiler checks the effective language version (derived from go.mod's go directive or the -lang compiler flag) via types.AllowsGoVersion(1, 16). If the version is below 1.16 and an embed directive is encountered on a var declaration, this error is returned with the current -lang value.

Source

Thrown at src/cmd/compile/internal/noder/noder.go:476

	renameinitgen++
	return s
}

func checkEmbed(decl *syntax.VarDecl, haveEmbed, withinFunc bool) error {
	switch {
	case !haveEmbed:
		return errors.New("go:embed requires import \"embed\" (or import _ \"embed\", if package is not used)")
	case len(decl.NameList) > 1:
		return errors.New("go:embed cannot apply to multiple vars")
	case decl.Values != nil:
		return errors.New("go:embed cannot apply to var with initializer")
	case decl.Type == nil:
		// Should not happen, since Values == nil now.
		return errors.New("go:embed cannot apply to var without type")
	case withinFunc:
		return errors.New("go:embed cannot apply to var inside func")
	case !types.AllowsGoVersion(1, 16):
		return fmt.Errorf("go:embed requires go1.16 or later (-lang was set to %s; check go.mod)", base.Flag.Lang)

	default:
		return nil
	}
}

View on GitHub (pinned to b6b368adc5)

Solutions

Update go.mod to go 1.16 or higher: edit the go directive to 'go 1.21' (or your toolchain version)
Remove any explicit -lang compiler flag or set it to go1.16+
If you cannot raise the language version, remove the embed directives and load files at runtime with os.ReadFile

Example fix

// before (go.mod)
go 1.15

// after (go.mod)
go 1.21

Defensive patterns

Strategy: validation

Validate before calling

// Check go.mod version supports embed before using it
import (
    "os"
    "strings"
)

func checkGoModVersion() (major, minor int, err error) {
    data, err := os.ReadFile("go.mod")
    if err != nil {
        return 0, 0, err
    }
    for _, line := range strings.Split(string(data), "\n") {
        line = strings.TrimSpace(line)
        if strings.HasPrefix(line, "go ") {
            v := strings.TrimPrefix(line, "go ")
            parts := strings.Split(v, ".")
            if len(parts) >= 2 {
                fmt.Sscanf(parts[0], "%d", &major)
                fmt.Sscanf(parts[1], "%d", &minor)
                return major, minor, nil
            }
        }
    }
    return 0, 0, fmt.Errorf("no go directive in go.mod")
}

// Usage: ensure major > 1 || (major == 1 && minor >= 16) before using embed

Prevention

Always set go.mod's go directive to at least the version that introduced the features you use
Keep go.mod's go directive updated when upgrading your Go toolchain
Do not pass -lang explicitly in build scripts unless necessary — let go.mod control it
Document minimum Go version requirements in your project README

When it happens

Trigger: A go.mod file declaring go 1.15 or lower combined with //go:embed directives in source files. Also triggered by explicitly passing -lang go1.15 (or lower) to the compiler while using embed directives.

Common situations: Adding embed directives to an existing project without updating go.mod's go directive. Working in a monorepo or vendored dependency where the language version is pinned below 1.16. CI pipelines that pass -lang explicitly.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/afec3d5294a6e466. Report an issue: GitHub.