go and parsing token with jwt-go

Question

Could anyone tell me why the following (from https://github.com/dgrijalva/jwt-go) example doesn't work?

token, err := jwt.Parse(myToken, func(token *jwt.Token) ([]byte, error) {
    return myLookupKey(token.Header["kid"])
})

if err == nil && token.Valid {
    deliverGoodness("!")
} else {
    deliverUtterRejection(":(")
}

I get an error saying cannot use func literal (type func(*jwt.Token) ([]byte, error)) as type jwt.Keyfunc in argument to jwt.Parse

I've tried to use the code from couple of different jwt-go examples but always ended up with this same error.

Answer 1

The function Parse expects

type Keyfunc func(*Token) (interface{}, error)

You need to return interface{}, not byte[] in your function literal.
(maybe using a byte.Buffer to wrap the byte[], that you can then read as in "Convert arbitrary Golang interface to byte array")

Gert Cuykens points out in the comments to issue 36: commit e1571c8 should have updated the example.
Other examples like this gist also need to be updated.