Команда установлена как $HOME/go/bin/shfmt
(если не указан GOBIN, то это $GOBIN/shfmt
):
$ go help install
usage: go install [-i] [build flags] [packages]
Install compiles and installs the packages named by the import paths.
Executables are installed in the directory named by the GOBIN environment
variable, which defaults to $GOPATH/bin or $HOME/go/bin if the GOPATH
environment variable is not set.