Method injection is everywhere. You probably use it every day and you don't even realize it. Have you ever written code like this?:
fmt.Fprint(os.Stdout, "Hello World")
How about this?:
req, err := http.NewRequest("POST", "/login", body)
This is method injection—the passing in of the dependency as a parameter to the request.
Let's examine the previous examples in more detail. The function signature for Fprint() is as follows:
// Fprint formats using the default formats for its operands and writes
// to w. It returns the number of bytes written and any write error
// encountered.
func Fprint(w io.Writer, a ...interface{}) (n int, err error)
As you can see, the first parameter, io.Writer, is a dependency for this function. What makes this different from any other function call is the fact that the dependency provides...
