moul http2curl: :triangular_ruler: Convert Golang’s http Request to CURL command line

Then, we specify the URL in the second parameter and the body to hold the data — or nil in the case of a GET request because we do not have a body to send. You’ll see the same output for these requests as you did for the requests on port 3333 being served by serverOne. By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. To build a command-line tool like “curl” you will need to use a number of go packages (e.g. for flag parsing and HTTP request handling) but presumably you can find what you need from the (excellent) docs.

Then, you created a const string value called keyServerAddr to act as the key for the HTTP server’s address value in the http.Request context. Lastly, you updated both your getRoot and getHello functions to access the http.Request’s context.Context value. Once you have the value, you include the HTTP server’s address in the fmt.Printf output so you can see which of the two servers handled the HTTP request. Many websites have forms they ask their users to fill out, so in the next section, you’ll update your program to read form data in addition to the request body and query string you already have.

  • The next update is to create your own http.Client instance in the client variable.
  • This information can be useful for troubleshooting issues if your client or server isn’t acting the way you expect.
  • First, you used the http.Get function to make a GET request to the server using only the server’s URL.
  • The output for the first query string value shows the Has method returned true because first has a value, and also that Get returned the value of 1.

In this section, you created a new HTTP server program using http.HandleFunc and http.ListenAndServe to run and configure the default server. Then, you updated it to use an http.ServeMux for the http.Handler instead of the default server multiplexer. Finally, you updated your program to use http.Server to run multiple HTTP servers in the same program. At the end of the function, you call cancelCtx to cancel the context being provided to the HTTP handlers and both server BaseContext functions. This way, if the server ends for some reason, the context will end as well. Many developers spend at least some of their time creating servers to distribute content on the internet.

Reading a Request Body

For now, in both of your HTTP handlers, you use fmt.Printf to print when a request comes in for the handler function, then you use the http.ResponseWriter to send some text to the response body. The http.ResponseWriter is an io.Writer, which means you can use anything capable of writing to that interface to write to the response body. In this case, you’re using the io.WriteString function to write your response to the body. Finally, the last change in the output is that the server is showing the request body it received from the client. The server could then use the encoding/json package to parse the JSON data the client sent and formulate a response. On the first line of output, the server prints that it received a GET request from your client for the / path.

  • Then, you created a const string value called keyServerAddr to act as the key for the HTTP server’s address value in the http.Request context.
  • You don’t need to make any other changes here because you’ve been calling Do on an http.Client value the whole time.
  • Many developers keep their projects in a directory to keep them organized.
  • In this section, you will create an initial program using http.Get to make an HTTP request, and then you will update it to use an http.Request with the default HTTP client.
  • I tried reading more about the difference between the two and feel that the curl should have worked.
  • The HTTP protocol uses more than just GET requests to communicate between programs, though.

Finally, you updated your server to return form validation information to the client using a custom HTTP header and a “Bad Request” status code. In this tutorial, you will create an HTTP server using Go’s standard library and then expand your server to read data from the request’s query string, the body, and form data. You’ll also update your program to respond to the request with your own HTTP headers and status codes. In this update, when myName is an empty string, instead of setting a default name of HTTP, you send the client an error message instead. First, you use the w.Header().Set method to set an x-missing-field header with a value of myName in the response HTTP headers.

Someone decided to add a second line encompassing the date to the API response which this installer does not expect. Whereas, curl doesn’t follow redirects by default (but golang curl has a default max of 50). We’ll use the standard Go client from the net/http library to initialize an HTTP client by simply creating a variable of type http.Client.

In Go, most of the HTTP functionality is provided by the net/http package in the standard library, while the rest of the network communication is provided by the net package. The net/http package not only includes the ability to make HTTP requests, but also provides an HTTP server you can use to handle those requests. In this update, you access the http.Request headers using req.Header, and then set the value of the Content-Type header on the request to application/json. The application/json media type is defined in the list of media types as the media type for JSON.

DigitalOcean makes it simple to launch in the cloud and scale up as you grow – whether you’re running one virtual machine or ten thousand. The series covers a number of Go topics, from installing Go for the first time to how to use the language itself.

The first error you’re checking for, http.ErrServerClosed, is returned when the server is told to shut down or close. This is usually an expected error because you’ll be shutting down the server yourself, but it can also be used to show why the server stopped in the output. If this happens, it will print the error to the screen and then exit the program with an error code of 1 using the os.Exit function. The Go standard library provides excellent support for HTTP clients in the net/http package. Throughout this guide, we’ll explore all the configurations a Go program needs to make HTTP/HTTPS requests to external resources. Your http.ListenAndServe function also passes a nil value for the http.Handler parameter.

Source Files

The Hypertext Transfer Protocol (HTTP) serves much of this content, whether it’s a request for a cat image or a request to load the tutorial you’re reading now. The Go standard library provides built-in support for creating an HTTP server to serve your web content or making HTTP requests to those servers. You’ll see there’s a value from the server for content-type, and there’s a Content-Type header being sent by the client. This is how you could have the same HTTP request path serving both a JSON and an XML API at the same time. By specifying the request’s content type, the server and the client can interpret the data differently. Your HTTP server is set up to use fmt.Printf to print information about incoming requests whenever the root / path is requested.

Listening for Requests and Serving Responses

The Body is an io.ReadCloser value, a combination of io.Reader and io.Closer, which means you can read the body’s data using anything that can read from an io.Reader value. The ioutil.ReadAll function is useful because it will read from an io.Reader until it either gets to the end of the data or encounters an error. Then it will either return the data as a []byte value you can print using fmt.Printf, or the error value it encountered.

And in The below line, I have replaced the GET with the POST, as this request will be in POST method. In the last parameter, we have passed the payload variable instead of nil.And the rest of the code is same so as an explanation. In the above code, the highlighted line shows how to add a header in the request and the rest of the explanation is same as above.


To provide more information about the data being sent over HTTP, the protocol includes HTTP headers, and one of those important headers is the Content-Type header. This header tells the server (or client, depending on the direction of the data) how to interpret the data it’s receiving. In this section, you will update your program to send your request as a POST request instead of a GET request. Your POST request will include a request body, and you will update your server to print out more information about the requests you’re making from the client. It’s also important to be sure you’re setting headers and sending the status code in the right order.

If the request succeeds, your program will print out that it got a response and the HTTP status code it received. In this tutorial, you will create a program that makes several types of HTTP requests to an HTTP server. Finally, you will customize your POST request to include an HTTP header and add a timeout that will trigger if your request takes too long. In this section, you updated your HTTP server to add validation to the /hello form input. If a name isn’t sent as part of the form, you used w.Header().Set to set a header to send back to the client. Once the header is set, you used w.WriteHeader to write the headers to the client, as well as a status code indicating to the client it was a bad request.

In this example, the value is represented as a []byte instead of the standard string because if you use the encoding/json package to encode JSON data, it will give you a []byte back instead of a string. The output for the first query string value shows the Has method returned true because first has a value, and also that Get returned the value of 1. The output for second shows that Has returned true because second was included, but the Get method didn’t return anything other than an empty string. You can also try making different requests by adding and removing first and second or setting different values to see how it changes the output from those functions.

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