Golang Study Notes

gistfile1.txt

My Golang study note

21/2 - Focus on today is error handling in Go

Back to Golang learning - learning about error handling in Go:
https://blog.golang.org/error-handling-and-go

Sharing with the group:

• Afaik, there is no repl - use Golang playground
• Error handling in Go:

https://play.golang.org/p/Mv7FADkEz9V
https://blog.golang.org/error-handling-and-go

My takeaway:

• I kinda like that the a method that raises an error need to do that explicitly, that is they need to return the error as part of the function return. In Go - by design, you need to explicitly check for errors - different from other languages that throw exception and "sometimes" catching them.
• The need to explicitly handle error will make your code verbose - in that blog post, it proposes a way to avoid that by introducing an error handler -> but I don't really get it.
• You can use fmt.Errorf to format string according to Printf rules and returns it as error for example:
  return 0, fmt.Errorf("math: %g", f)
• Create your own error type by "implementing" error interface - I am not too familiar with interface yet, so need to read up more about it. But at high level, it just means create a type that has an "Error()" method.
  Here is an example:

type NegativeSqrtError float64

func (f NegativeSqrtError) Error() string {
    return fmt.Sprintf("math: square root of negative number %g", float64(f))
}

Further questions:

• How is interface works in Go?
• What is a type in Go? And how is it different to structure?

22/2

dep -> dependency management in go https://github.com/golang/dep - does blue team use this?

started following gowebexamples.com
unable to start web server on port 80 - wondering why, using log.Fatal helps
log.Fatal(http.ListenAndServe(":80", nil))

Middleware

TIL: you can pass in a function as a param to a function.
A function has a type - the type is determined by the function signature.

func logging(f http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		log.Println(r.URL.Path)
		f(w, r)
	}
}

https://gowebexamples.com/basic-middleware/

Basically middleware is just a function that takes http.HandlerFunc and return http.HandlerFunc

Advanced Middleware

create a middleware type
type Middleware func(http.HandlerFunc) http.HandlerFunc
and you can chain em - you need to create your own Chain method urgh