Project Layout

Small and simple projects can have all their code in one directory:

project-root-directory/
  go.mod
  modname.go
  modname_test.go

Large server project example:

project-root-directory/
  go.mod
  internal/
    auth/
      ...
    metrics/
      ...
    model/
      ...
  cmd/
    api-server/
      main.go
    metrics-analyzer/
      main.go
    ...
  ... the project's other directories with non-Go code

For more information about the layout, see Organizing a Go module and Standard Go Project Layout.