### Per-file SPDX header example

Source: https://github.com/hstern/go-subjectid/blob/main/AGENTS.md

Every .go file must start with a SPDX header.

```go
// Copyright 2026 The go-subjectid Authors
// SPDX-License-Identifier: Apache-2.0

package subjectid
```

--------------------------------

### Install

Source: https://github.com/hstern/go-subjectid/blob/main/README.md

Install the go-subjectid library.

```sh
go get github.com/hstern/go-subjectid@latest
```

--------------------------------

### Quickstart: Build and marshal

Source: https://github.com/hstern/go-subjectid/blob/main/README.md

Build a Subject Identifier value in Go and emit canonical wire bytes.

```go
package main

import (
	"encoding/json"
	"fmt"

	"github.com/hstern/go-subjectid"
)

func main() {
	id := subjectid.IssSubID{
		Iss: "https://issuer.example.com/",
		Sub: "145234573",
	}
	if err := id.Validate(); err != nil {
		panic(err)
	}
	out, err := json.Marshal(id)
	if err != nil {
		panic(err)
	}
	fmt.Println(string(out))
	// {"format":"iss_sub","iss":"https://issuer.example.com/","sub":"145234573"}
}
```

--------------------------------

### SPDX Header Example

Source: https://github.com/hstern/go-subjectid/blob/main/README.md

Example of the SPDX header comment found in source files.

```go
// Copyright 2026 The go-subjectid Authors
// SPDX-License-Identifier: Apache-2.0
```

--------------------------------

### Quickstart: Decode and validate

Source: https://github.com/hstern/go-subjectid/blob/main/README.md

Decode a Subject Identifier from JSON, validate it, and act on the result.

```go
package main

import (
	"encoding/json"
	"fmt"

	"github.com/hstern/go-subjectid"
)

func main() {
	wire := []byte(`{"format":"email","email":"user@example.com"}`)

	id, err := subjectid.Parse(json.RawMessage(wire))
	if err != nil {
		panic(err)
	}
	if err := id.Validate(); err != nil {
		panic(err)
	}
	fmt.Printf("%s identifier: %#v\n", id.Format(), id)
}
```

--------------------------------

### Custom Subject Identifier Format

Source: https://github.com/hstern/go-subjectid/blob/main/README.md

Example of defining a new Go type embedding subjectid.Seal and registering a constructor for a custom format.

```go
type OrgTenantID struct {
	subjectid.Seal
	Tenant string
}

func (OrgTenantID) Format() string                   { return "org.example.tenant" }
func (OrgTenantID) Validate() error                  { /* … */ return nil }
func (o OrgTenantID) MarshalJSON() ([]byte, error)   { /* spec-order */ }
func (o *OrgTenantID) UnmarshalJSON(b []byte) error  { /* … */ }

func init() {
	_ = subjectid.RegisterFormat("org.example.tenant",
		func() subjectid.SubjectIdentifier { return &OrgTenantID{} })
}
```

--------------------------------

### Build prerequisites

Source: https://github.com/hstern/go-subjectid/blob/main/README.md

Build the pap CLI for regenerating validation regexes.

```sh
git clone --depth=1 https://github.com/pandatix/go-abnf.git /tmp/go-abnf
go build -C /tmp/go-abnf/cmd/pap -o "$(go env GOPATH)/bin/pap"
```

--------------------------------

### Quick checks before pushing

Source: https://github.com/hstern/go-subjectid/blob/main/AGENTS.md

These commands should be run before pushing code to ensure code quality and correctness.

```sh
gofmt -l .
go vet ./...
go mod tidy -diff
go test -race -shuffle=on ./...
golangci-lint run ./...
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.