A service to highlight a decent application structure in Go.
The cmd and pkg packages included follow the community standards in Go.
The cmd package contain server or command-lne versions of the application.
The pkg package contain all other project specific files.
Under the pkg package we have the domain package which contains structs for the various entities in the application. It also includes a contract (an Interface) for the Storage/Repository layer to follow.
Moving on, we have the storage sub-package which contains various storage implementations for the application. Observe that each implementation has its own folder to ensure package level privacy, and they implement the interface specified by the models.
Included also is the service package (excluded at times), which contains various domain level functions which aren't to be implemented by a single entity alone. They use the contracts defined by the domain and inject the storage/repo implementation at runtime for functions that involve storage. They also define interfaces to be used by handlers/controllers that implement them. Observe that for this particular project services are divided according to the domain (i.e user, courier), for other applications they're divided according to application context (i.e in a beer reviewing app - the context could be adding, listing and reviewing). Note that the repository and service interface have to be in sync with this division.
Finally, the http package specifies the handler for the application. They make use of the services to function. Note that this package is further divided based on the architecture you desired to use e.g rest, rpc, e.t.c. You could also include a top-level handler/controller folder, if you desire different protocols in your application.