chore: sort import statements

[0xHansLee]

There are some unsorted import statements, so I sorted them using goimports-reviser.

> goimports-reviser -rm-unused ./...

Currently, goimports do not sort import statements consistently (it is well-known issue: golang/go#20818).

There are many other alternatives, and I tried to use goimports-reviser since it works well as we desired and they also have linter for sorting import statements (we can add linter to CI in the future as well).

FYI, you can configure goimports-reviser in IntelliJ as described here.

[chokobole]

LGTM

[seolaoh]

LGTM

[0xHansLee]

Let me share how to set goimports-reviser formatter on save in VS code.
(I'm not sure this is the best way, but I want to share how to figure it out. If you have any better idea, please leave your tips for everyone.)

I used run on save extenstion to run goimports-reviser command on save.
This is the configuration added to settings.json

{
    // ...
    "emeraldwalk.runonsave": {
        "commands": [
            {
                "match": ".*",
                "cmd": "$HOME/go/bin/goimports-reviser -rm-unused ${file}"
            },
        ]
    }
    // ...
}