missinglicense is a simple tool that lists all of your public GitHub repositories that are missing a LICENSE file.
Installation is simple and no different to any Go tool. The only requirement is a working Go install.
go get go.tmthrgd.dev/missinglicense
Usage is simple with the missinglicense command requiring only the GITHUB_TOKEN environment variable to be set.
missinglicense
You need to set the GITHUB_TOKEN environment variable to a valid GitHub personal access token with public_repo scope. See Authenticating with GraphQL and Creating a personal access token for instructions on creating a token.
missinglicense does not check that the LICENSE file is valid or recognised, merely that it exists. It handles both LICENSE and LICENSE.md files.