[Golang] – Consuming REST API

Following examples to consuming a REST API by using the lib net/http.

NOTE: You will find how to convert the Golang struct to JSON format as the response in JSON format to the Golang struct as well.

Struct Example

The following struct will be used as an example to manipulated the data.

//Struct example
type Client struct{
   Name                  string     `json:"name"`
   Address               string     `json:"address"`
   Orders                []Order    `json:"order,omitempty"`
}

POST Example

The following example will show how to transform an instance of a Golang struct/object in JSON format to do the request as well.

   // Create the object and parse for JSON
   clientJSON, err := json.Marshal(client)
   if err != nil {
      fmt.Errorf("Error to transform the client struct in JSON", "client", client, "Error", err)
   }

   //Create the POST request
   url:= "http://myrestservice/api/clients"
   req, err := http.NewRequest(http.MethodPost, url , strings.NewReader(string(clientJSON)))
   req.Header.Set("Content-Type", "application/json")
   if err != nil {
      fmt.Errorf("Error when try to create the request", "HTTPMethod", http.MethodPost, "Request", req, "url", url, "error", err)
   }

   //Do the request
   client := &http.Client{}
   response, err := client.Do(req)
   if err != nil {
      fmt.Errorf(Error when try to do the request", "HTTPMethod", http.MethodPost, "Request", req, "Response", response, "url", url, "error", err)
   }
   defer response.Body.Close()

DELETE Example

//Create the DELETE request
url:= "http://myrestservice/api/clients/2" 
req, err := http.NewRequest(http.MethodDelete, url ,nil)
req.Header.Set("Content-Type", "application/json")
if err != nil {
   fmt.Errorf("Error when try to create the request", "HTTPMethod", http.MethodDelete, "Request", req, "url", url, "error", err)
}

//Do the request
client := &http.Client{}
response, err := client.Do(req)
defer response.Body.Close()

if err != nil {
   fmt.Errorf("Error when try to do the request", "HTTPMethod", http.MethodDelete, "Request", req, "url", url, "error", err)
}

GET Example

The following example will show how to transform the request JSON response in the Golang struct as well.

// Fill the record with the data from the JSON
// Transform the body request in the version struct
got := models.Client{}

//Create the GET request
url:= "http://myrestservice/api/clients/2" 
req, err := http.NewRequest(http.MethodGet,  url, nil)
req.Header.Set("Content-Type", "application/json")
if err != nil {
   fmt.Errorf("Error when try to create the request", "HTTPMethod", http.MethodGet, "Request", req, "url", url, "error", err)
}

//Do the request
client := &http.Client{}
response, err := client.Do(req)
defer response.Body.Close()

if err != nil {
   fmt.Errorf("Error when try to do the request", "HTTPMethod", http.MethodGet, "Request", req, "url", url, "error", err)
}

if 200 != response.StatusCode {
  fmt.Errorf("The client was not found in the REST Service API", "HTTPMethod", http.MethodGet, "url", url)
}

//To transform the response in the struct
var obj models.Client
err = json.NewDecoder(response.Body).Decode(&obj)
if err != nil {
   fmt.Errorf("Error when try to decoder the body response", "HTTPMethod", http.MethodGet, "Request", req, "Response", response, "url", url, "error", err)
}