How to Reuse HTTP Request Bodies in Go Chi Middleware Handlers?

Reusing HTTP Request Bodies in Go Chi Middleware Handlers

In Go, when using the go-chi HTTP router, you may encounter a situation where you need to reuse the request body in multiple middleware handlers. The following code snippet illustrates a scenario where this issue arises:

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
}

The Registration handler attempts to read the request body and process it. However, after this step, when the Create handler is called, it fails to parse JSON from the request body due to it being empty. This happens because the Outer handler reads the request body to its end, leaving nothing to read for the inner handler.

To resolve this issue, the request body must be restored by restoring the data read earlier in the outer handler. The following code snippet demonstrates how to achieve this:

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)
}

In this code, the bytes.NewReader function returns an io.Reader on a byte slice. The io.NopCloser function, in turn, converts the io.Reader to the required io.ReadCloser for r.Body. By restoring the request body, subsequent handlers can access and process its contents as expected.

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