pub unsafe extern "C" fn SSL_CTX_set_next_proto_select_cb(
    ctx: *mut SSL_CTX,
    cb: Option<unsafe extern "C" fn(ssl: *mut SSL, out: *mut *mut u8, out_len: *mut u8, in_: *const u8, in_len: c_uint, arg: *mut c_void) -> c_int>,
    arg: *mut c_void
)