[Go 1.21] Replace 'any' / 'interface{}' implementation with Generics (#…

…54)

* gobreaker/v2: added generics implementation in v2 module

* gobreaker/v2/example: added v2 example

* gobreaker/README: updated README.md

* fixup! gobreaker/v2: added generics implementation in v2 module

---------

Co-authored-by: Yoshiyuki Mineo <[email protected]>

README.md

@@ -90,10 +90,38 @@ Otherwise, `Execute` returns the result of the request.
 If a panic occurs in the request, `CircuitBreaker` handles it as an error
 and causes the same panic again.
 
+
+V2 Implementation
+---
+
+The [v2 implementation](./v2) provides the same CircuitBreaker logic, but with support for generics in Go.
+
+This change allows for CircuitBreaker instances to specify the handled type directly, and skips type-casting an `any` 
+or `interface{}` type into the desired target one.
+
+This change mostly focuses on the [CircuitBreaker's Execute](./v2/gobreaker.go#L228) method, which accepts an 
+executable function of a given type:
+
+```go
+func (cb *CircuitBreaker[T]) Execute(req func() (T, error)) (T, error) 
+```
+
+
 Example
 -------
 
+> *v1 Example*
+
 ```go
+import (
+  "fmt"
+  "io"
+  "log"
+  "net/http"
+
+  "github.com/sony/gobreaker"
+)
+
 var cb *breaker.CircuitBreaker
 
 func Get(url string) ([]byte, error) {
@@ -119,6 +147,45 @@ func Get(url string) ([]byte, error) {
 }
 ```
 
+
+> *v2 Example*
+
+
+```go
+import (
+  "fmt"
+  "io"
+  "log"
+  "net/http"
+
+  "github.com/sony/gobreaker/v2"
+)
+
+var cb *gobreaker.CircuitBreaker[[]byte]
+
+func Get(url string) ([]byte, error) {
+  body, err := cb.Execute(func() ([]byte, error) {
+    resp, err := http.Get(url)
+    if err != nil {
+      return nil, err
+    }
+
+    defer resp.Body.Close()
+    body, err := io.ReadAll(resp.Body)
+    if err != nil {
+      return nil, err
+    }
+
+    return body, nil
+  })
+  if err != nil {
+    return nil, err
+  }
+
+  return body, nil
+}
+```
+
 See [example](https://github.com/sony/gobreaker/blob/master/example) for details.
 
 License

v2/example/http_breaker.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+
+	"github.com/sony/gobreaker/v2"
+)
+
+var cb *gobreaker.CircuitBreaker[[]byte]
+
+func init() {
+	var st gobreaker.Settings
+	st.Name = "HTTP GET"
+	st.ReadyToTrip = func(counts gobreaker.Counts) bool {
+		failureRatio := float64(counts.TotalFailures) / float64(counts.Requests)
+		return counts.Requests >= 3 && failureRatio >= 0.6
+	}
+
+	cb = gobreaker.NewCircuitBreaker[[]byte](st)
+}
+
+// Get wraps http.Get in CircuitBreaker.
+func Get(url string) ([]byte, error) {
+	body, err := cb.Execute(func() ([]byte, error) {
+		resp, err := http.Get(url)
+		if err != nil {
+			return nil, err
+		}
+
+		defer resp.Body.Close()
+		body, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return nil, err
+		}
+
+		return body, nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return body, nil
+}
+
+func main() {
+	body, err := Get("http://www.google.com/robots.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(string(body))
+}

v2/go.mod

@@ -0,0 +1,11 @@
+module github.com/sony/gobreaker/v2
+
+go 1.21
+
+require github.com/stretchr/testify v1.8.4
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

v2/go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=