Function jsonwebtoken::decode_header

pub fn decode_header(token: &str) -> Result<Header>

Decode a JWT without any signature verification/validations and return its Header.

If the token has an invalid format (ie 3 parts separated by a .), it will return an error.

use jsonwebtoken::decode_header;

let token = "a.jwt.token".to_string();
let header = decode_header(&token);