Hands-On Dependency Injection in Go

Introducing providers

The documentation defines a provider as follows:

"A function that can produce a value."

For our purposes, we can put it a different way—a provider returns an instance of a dependency. 

The simplest form a provider can take is a simple no argument function, as shown in the following code:

// Providerfunc ProvideFetcher() *Fetcher {   return &Fetcher{}}// Object being "provided"type Fetcher struct {}func (f *Fetcher) GoFetch() (string, error) {

return "", errors.New("not implemented yet")}

Providers can also indicate that they require dependencies to be injected by having parameters like this:

func ProvideFetcher(cache *Cache) *Fetcher {   return &Fetcher{      cache: cache,   }}

The dependencies (parameters) of this provider ...