mismatch of EIP712Domain type definition and actual data

[youjinchoi]

when testing eth_signTypedData, this is the part of the request:

{
    "types": {
        "EIP712Domain": [
            {
                "name": "name",
                "type": "string"
            },
            {
                "name": "version",
                "type": "string"
            },
            {
                "name": "verifyingContract",
                "type": "address"
            }
        ],
        "RelayRequest": [
            {
                "name": "target",
                "type": "address"
            },
            {
                "name": "encodedFunction",
                "type": "bytes"
            },
            {
                "name": "gasData",
                "type": "GasData"
            },
            {
                "name": "relayData",
                "type": "RelayData"
            }
        ],
        "GasData": [
            {
                "name": "gasLimit",
                "type": "uint256"
            },
            {
                "name": "gasPrice",
                "type": "uint256"
            },
            {
                "name": "pctRelayFee",
                "type": "uint256"
            },
            {
                "name": "baseRelayFee",
                "type": "uint256"
            }
        ],
        "RelayData": [
            {
                "name": "senderAddress",
                "type": "address"
            },
            {
                "name": "senderNonce",
                "type": "uint256"
            },
            {
                "name": "relayWorker",
                "type": "address"
            },
            {
                "name": "paymaster",
                "type": "address"
            }
        ]
    },
    "domain": {
        "name": "GSN Relayed Transaction",
        "version": "1",
        "chainId": 42,
        "verifyingContract": "0x6453D37248Ab2C16eBd1A8f782a2CBC65860E60B"
    },
    "primaryType": "RelayRequest",
    "message": {
        "target": "0x9cf40ef3d1622efe270fe6fe720585b4be4eeeff",
        "encodedFunction": "0xa9059cbb0000000000000000000000002e0d94754b348d208d64d52d78bcd443afa9fa520000000000000000000000000000000000000000000000000000000000000007",
        "gasData": {
            "gasLimit": "39507",
            "gasPrice": "1700000000",
            "pctRelayFee": "70",
            "baseRelayFee": "0"
        },
        "relayData": {
            "senderAddress": "0x22d491bde2303f2f43325b2108d26f1eaba1e32b",
            "senderNonce": "3",
            "relayWorker": "0x3baee457ad824c94bd3953183d725847d023a2cf",
            "paymaster": "0x957F270d45e9Ceca5c5af2b49f1b5dC1Abb0421c"
        }
    }
}

types > EIP712Domain has 3 elements, while the actual domain has additional data chainId. it throws an error to generate hash to be signed due to this mismatch. fyi we are using go-ethereum for the hash generation.