Hi @hunght,
The command, cd badger && go install will install badger and create a binary with the name badger inside directory pointed by $GOBIN. It is usually set to ~/go/bin
To run badger through terminal, you can either run the badger executable inside GOBIN or add directory containing badger executable to $PATH variable.
Related link: linux - How to properly set Environment variables (golang on Manjaro) - Unix & Linux Stack Exchange