How to Reuse HTTP Request Body Data Across Go-chi Middleware Handlers?

Reusing HTTP Request Body in Go-chi Middleware Handlers

When using go-chi for HTTP routing, it's convenient to reuse code in multiple handlers. However, this can lead to unexpected issues if the handlers rely on request body data.

Consider the following scenario:

func Registration(w http.ResponseWriter, r *http.Request) {
    b, err := ioutil.ReadAll(r.Body) // if you delete this line, the user will be created   
    // ...other code

    // if all good then create new user
    user.Create(w, r)
}

...

func Create(w http.ResponseWriter, r *http.Request) {
  b, err := ioutil.ReadAll(r.Body)  
  // ...other code

  // ... there I get the problem with parse JSON from &b
}

In this example, both the Registration and Create handlers attempt to read the request body using ioutil.ReadAll. However, since Registration reads the body to its end, there's no data left to read when Create is called.

To resolve this issue, the outer handler (Registration) must restore the request body with the data read previously. This can be achieved using the following code:

func Registration(w http.ResponseWriter, r *http.Request) {
    b, err := io.ReadAll(r.Body) 
    // ...other code
    r.Body = io.NopCloser(bytes.NewReader(b))
    user.Create(w, r)
}

Here, the bytes.NewReader() function returns an io.Reader on a byte slice, while the io.NopCloser function converts this reader to the io.ReadCloser interface required for r.Body. By resetting r.Body with the original data, Create can now access and parse the request body as expected.

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