With jq command, I want to merge multiple json files.

But I have no idea how to achieve below expectation.

a.json

{
    "key1": {
        "key2": [
            1,
            2
        ]
    },
    "key3": "aaa"
}

b.json

{
    "key1": {
        "key2": [
            3,
            4,
            5
        ]
    },
    "key4": "bbb"

expected result

{
    "key1": {
        "key2": [
            1,
            2,
            3,
            4,
            5
        ]
    },
    "key3": "aaa",
    "key4": "bbb"
}