jwt

jwt issues and verifies compact JSON Web Tokens, deliberately limited to HS256. It follows the JWS compact serialization (RFC 7515) and the registered claims (RFC 7519), but supports exactly one algorithm with strict defaults - a smaller surface is a safer surface. Zero dependencies, standard library only.

Install

go get github.com/goloop/jwt

Sign

token, err := jwt.Sign(jwt.Claims{
	Subject:   "user-123",
	Issuer:    "api",
	Audience:  jwt.Audience{"web"},
	ExpiresAt: time.Now().Add(time.Hour).Unix(),
	IssuedAt:  time.Now().Unix(),
	Extra:     map[string]any{"role": "admin"},
}, key)

The header is always {"alg":"HS256","typ":"JWT"}. Custom claims go in Claims.Extra.

Verify

claims, err := jwt.Verify(token, key,
	jwt.WithIssuer("api"),
	jwt.WithAudience("web"),
	jwt.WithLeeway(30*time.Second),
)

Verify:

• requires alg=HS256 (rejects none, RS256, everything else);
• requires a present exp;
• verifies the signature in constant time before interpreting the payload;
• checks exp/nbf/iat with optional leeway, and issuer/audience when set.

Key rotation

claims, err := jwt.Verify(token, newKey, jwt.WithKey(oldKey))

Tokens are signed with the primary key; verification accepts any configured key.

Not supported (by design)

RS/ES/PS algorithms, none, JWE encryption, JWKS, and parsing without signature verification.

Documentation

• English reference: DOC.md
• Ukrainian reference: DOC.UK.md

License

MIT - see LICENSE.