E0407: No provider for a dependency
A handler, a hook, a cron, a service or a constructor takes a pointer or interface the container doesn't have. The message says who needs it, at its file and line, and names the parameter and its type. Reported at boot.
Wrong
go
func OpenDB() (*DB, error) { … }
app := web.New() // ListPets takes a *DBRight
go
func OpenDB() (*DB, error) { … }
app := web.New(web.Provide(OpenDB))