updates HttpPostJSON to support response decoding (#7)

This is a breaking api change.

- Updated HttpPostJSON in json.go to handle JSON response decoding when content-type is JSON, with improved error handling and code clarity
- Added code in README to demonstrate HttpPutJSON and updated HttpPostJSON functionalities

.gitignore

@@ -2,3 +2,4 @@ app
 *.swp
 *.test
 *.out
+.DS_Store

README.md

@@ -56,7 +56,11 @@ func main() {
 
 	var data interface{}
 	err = gotoolbox.HttpGetJSON("https://api.example.com/data.json", &data)
-	err = gotoolbox.HttpPostJSON("https://api.example.com/data.json", data, http.StatusOK)
+
+	err = gotoolbox.HttpPutJSON("https://api.example.com/data.json", data)
+
+	var res Response
+	err = gotoolbox.HttpPostJSON("https://api.example.com/data.json", data, &res, http.StatusCreated)
 }
 ```
 

json.go

@@ -9,6 +9,9 @@ import (
 	"os"
 )
 
+const contentType = "Content-Type"
+const contentTypeJSON = "application/json"
+
 //ReadJSONFile reads JSON from a file
 func ReadJSONFile(fileName string) (map[string]string, error) {
 
@@ -51,7 +54,7 @@ func HttpGetJSON(url string, result interface{}) error {
 }
 
 // HttpPutJSON encodes a struct as JSON and
-// HTTP PUTs it to the specified endpoint
+// HTTP PUTs it to the specified url
 // returns an error if http response code is not 200
 func HttpPutJSON(url string, o interface{}) error {
 
@@ -61,7 +64,7 @@ func HttpPutJSON(url string, o interface{}) error {
 	if err != nil {
 		return err
 	}
-	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set(contentType, contentTypeJSON)
 	client := &http.Client{}
 	resp, err := client.Do(req)
 	if err != nil {
@@ -75,25 +78,35 @@ func HttpPutJSON(url string, o interface{}) error {
 }
 
 // HttpPostJSON encodes a struct as JSON and
-// HTTP POSTs it to the specified endpoint
-// returns an error if http response code does not match specified
-func HttpPostJSON(url string, o interface{}, httpStatusCodeToCheck int) error {
+// HTTP POSTs it to the specified url.
+// If the HTTP response's content-type is JSON,
+// then the response is decoded into the given result.
+// Returns an error if http response code does not match
+// specified `httpStatusCodeToCheck`.
+// Set `httpStatusCodeToCheck` == 0 to opt out of the check.
+func HttpPostJSON(url string, request, response interface{}, httpStatusCodeToCheck int) error {
 
 	payload := new(bytes.Buffer)
-	json.NewEncoder(payload).Encode(o)
+	json.NewEncoder(payload).Encode(request)
 	req, err := http.NewRequest(http.MethodPost, url, payload)
 	if err != nil {
 		return err
 	}
-	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set(contentType, contentTypeJSON)
 	client := &http.Client{}
 	resp, err := client.Do(req)
 	if err != nil {
 		return fmt.Errorf("unexpected http PUT error: %w", err)
 	}
 	defer resp.Body.Close()
-	if resp.StatusCode != httpStatusCodeToCheck {
+	if resp.StatusCode != 0 && resp.StatusCode != httpStatusCodeToCheck {
 		return fmt.Errorf("unexpected http POST status: %s", resp.Status)
 	}
+	if resp.Header.Get(contentType) == contentTypeJSON {
+		err = json.NewDecoder(resp.Body).Decode(response)
+		if err != nil {
+			return fmt.Errorf("cannot decode JSON: %w", err)
+		}
+	}
 	return nil
 }