How to get expiration date from jwt token in go?

In the Go language, JWT tokens are a common authentication mechanism. To get the expiration date from the JWT token, we can use the third-party library "github.com/dgrijalva/jwt-go" to parse the token's payload. First, we need to parse the token string into a jwt.Token object, and then we can get the expiration date by accessing the Token.Claims["exp"] field. The value of this field is a Unix timestamp, which can be converted to a time type using the time.Unix function. In this way, we can easily get the expiration date of the JWT token.

Question content

I have a jwt token and I can see the decoded token on the https://jwt.io/ website. It doesn't require me to set any secrets or claims. So I'm looking for a way to decode the token to get the expiration date without providing any secret.

I am using the library ngopkg.in/square/go-jose.v2/jwt and below is my code:

token, err := jwt.ParseSigned(jwtToken)

Return value token There is a header field which includes keyid, algorithm but it doesn't give me the expiration date.

I searched this topic and people said to use github.com/auth0/go-jwt-middleware/v2/validator library, but it requires setting the key/secret. Parse whether a secret is required for the token's expiration date. Website https://jwt.io/How to know the expiration date?

Workaround

Using the example jwt token from jwt.io, This code parses and retrieves claims with unverified signatures:

func main() {
    raw := "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c"

    t, err := jwt.ParseSigned(raw)
    if err != nil {
        panic(err)
    }

    var claims map[string]any
    if err := t.UnsafeClaimsWithoutVerification(&claims); err != nil {
        panic(err)
    }

    fmt.Println(claims)
}

In this example, the expiration time should appear as one of the fields in the claims mapping. To retrieve it, use exp, ok := claims["expire"] (depending on the exact name).

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