go-chain

go-chain is a dependency injection to create a function to call a group of function orderly.

Use case

Middleware for HTTP endpoints

func InitVars() (string, error) {
  return "", nil
}

func RequestContext(r *http.Request) context.Context {
  return r.Context()
}

func Auth(ctx context.Context, r *http.Request) error {
  return nil
}

func GetBody[T any] (r *http.Request) (ret T, err error) {
  err = json.NewDecoder(r.Body).Decode(&ret)
  return
}

func Handler(ctx context.Context, arg int) (string, error) {
  return fmt.Sprintf("%d", arg), nil
}

func Return[T any] (w http.ResponseWriter, arg T, err error) {
  if err != nil {
    w.WriteHeader(http.StatusInternalServerError)
    return
  }

  json.NewEncoder(w).Encode(arg)
}

func Server() {
  http.HandleFunc("/", chain.C[func(w http.ResponseWriter, r *http.Request)](
     InitVars, chain.Defer(Return[string]), RequestContext, Auth, GetBody[int], Handler,
  ))
}

The function generating by chain.C() is similar to:

func (w http.ResponseWriter, r *http.Request) {
  s, err := InitVars()
  if err != nil {
    return
  }

  defer Return[string](w, s, err)

  ctx := RequestContext(r)

  err = Auth(ctx, r)
  if err != nil {
    return
  }

  var i int
  i, err = GetBody[int](r)
  if err != nil {
    return
  }

  var s string
  s, err = Handler(ctx, i)
  if err != nil {
    return
  }
}

Bench

$ go test --test.bench .
goos: linux
goarch: amd64
pkg: github.com/googollee/go-chain
cpu: Intel(R) Xeon(R) W-2135 CPU @ 3.70GHz
BenchmarkC-12              70035             15660 ns/op
BenchmarkFunc-12          152092              7110 ns/op
PASS
ok      github.com/googollee/go-chain   2.474s