`go.mod file not found in current directory or any parent directory.` when `go get`

[AuroraTea]

> go get -u software.sslmate.com/src/go-pkcs12
go: go.mod file not found in current directory or any parent directory.            
        'go get' is no longer supported outside a module.                          
        To build and install a command, use 'go install' with a version,           
        like 'go install example.com/cmd@latest'                                   
        For more information, see https://golang.org/doc/go-get-install-deprecation
        or run 'go help get' or 'go help install'. 

[AuroraTea]

It's embarrassing, right? What was I thinking yesterday? It's not because there was a problem with the path I was on...